Pipe list of package-files through realpath, to resolve any symlinks

As of focal a bunch of top-level dirs are symlinks (eg /lib -> /usr/lib) but
the deb packages still deploy files to the symlink rather than the real dir.
Thus if we just take the contents of all the *.list files we end up not
excluding lots of files that are in fact provided by debs

ROOT/DEBIAN/control

@@ -3,7 +3,6 @@ Priority: optional
 Section: otherosfs
 Maintainer: Chemistry COs <support@ch.cam.ac.uk>
 Architecture: all
-Version: 0.9-ch72
+Version: 0.9-ch73
 Depends: zfs-dkms, postgresql-13 | postgresql-9.5 | postgresql-9.4 , liblockfile-simple-perl, libdbi-perl, libjson-perl, libzfs-perl-chem, libnet-openssh-perl, libdbd-pg-perl, mbuffer, rsync, nfs-kernel-server, pv, libwww-curl-perl
 Description: a backup system using ZFS (repository 'backup-scheduler')
- Ported (well, mostly) from FreeBSD to a Sane OS.

ROOT/etc/chem-zfs-backup-server/zfs-rsync.d/prepare

@@ -30,7 +30,7 @@ if $SSH root@$SERVER [ /var/lib/dpkg/status -nt /var/adm/backup/package-files ]
   dpkg --get-selections | awk ' { print \$1 ; } ' >/var/adm/backup/packages
   cat /var/lib/dpkg/info/*.list | while read F ; do [ -f \"\$F\" ] && echo \"\$F\" ; done | sort > \$FILELIST
   awk '/Description:/ { flag = 0 } ; flag == 1 { print \$1 ; }  ; /Conffiles:/ { flag = 1  } ; ' </var/lib/dpkg/status |  sort >\$CONFLIST
-  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// >/var/adm/backup/package-files
+  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// | xargs -n1 realpath >/var/adm/backup/package-files
   rm \$FILELIST \$CONFLIST
  "
  mkdir -p $CONFDIR/$SERVER

ROOT/etc/chem-zfs-backup-server/zfs-rsync.d/prepare-ignore-mysql

@@ -36,7 +36,7 @@ if $SSH root@$SERVER [ /var/lib/dpkg/status -nt /var/adm/backup/package-files ]
   dpkg --get-selections | awk ' { print \$1 ; } ' >/var/adm/backup/packages
   cat /var/lib/dpkg/info/*.list | while read F ; do [ -f \"\$F\" ] && echo \"\$F\" ; done | sort > \$FILELIST
   awk '/Description:/ { flag = 0 } ; flag == 1 { print \$1 ; }  ; /Conffiles:/ { flag = 1  } ; ' </var/lib/dpkg/status |  sort >\$CONFLIST
-  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// >/var/adm/backup/package-files
+  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// | xargs -n1 realpath >/var/adm/backup/package-files
   rm \$FILELIST \$CONFLIST
  "
  mkdir -p $CONFDIR/$SERVER

ROOT/etc/chem-zfs-backup-server/zfs-rsync.d/prepare-ignore-mysql-and-postgres

@@ -36,7 +36,7 @@ if $SSH root@$SERVER [ /var/lib/dpkg/status -nt /var/adm/backup/package-files ]
   dpkg --get-selections | awk ' { print \$1 ; } ' >/var/adm/backup/packages
   cat /var/lib/dpkg/info/*.list | while read F ; do [ -f \"\$F\" ] && echo \"\$F\" ; done | sort > \$FILELIST
   awk '/Description:/ { flag = 0 } ; flag == 1 { print \$1 ; }  ; /Conffiles:/ { flag = 1  } ; ' </var/lib/dpkg/status |  sort >\$CONFLIST
-  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// >/var/adm/backup/package-files
+  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// | xargs -n1 realpath >/var/adm/backup/package-files
   rm \$FILELIST \$CONFLIST
  "
  mkdir -p $CONFDIR/$SERVER

ROOT/etc/chem-zfs-backup-server/zfs-rsync.d/prepare2

@@ -26,7 +26,7 @@ if $SSH root@$SERVER [ /var/lib/dpkg/status -nt /var/adm/backup/package-files ]
   dpkg --get-selections | awk ' { print \$1 ; } ' >/var/adm/backup/packages
   cat /var/lib/dpkg/info/*.list | while read F ; do [ -f \"\$F\" ] && echo \"\$F\" ; done | sort > \$FILELIST
   awk '/Description:/ { flag = 0 } ; flag == 1 { print \$1 ; }  ; /Conffiles:/ { flag = 1  } ; ' </var/lib/dpkg/status |  sort >\$CONFLIST
-  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// >/var/adm/backup/package-files
+  diff -u \$FILELIST \$CONFLIST | grep ^-/ | sed s/^-// | xargs -n1 realpath >/var/adm/backup/package-files
   rm \$FILELIST \$CONFLIST
  "
  mkdir -p /etc/chem-zfs-backup-server/zfs-rsync.d/$SERVER