Fixed issue where backups from prior installs, with root-owned dirs,
will cause SDP upgrades to break due to root ownership of the
BackupBase and BackupDir folders. This occurs on systems that do
NOT have root squash enabled (and may not even be NFS), but do have
installs done with prior versions new enough to operate the
opt_perforce_sdp_backup.service.
This change executes 'chown' commands as root on the /hxdepots volume
which would fail if /hxdepots were mounted on NFS with root squash enabled.
However, this should not be an issue because prior installs could never
have occurred on systems with NFS with root squash enabled, because
installs did not work at all with NFS and root squash enabled until v2.11.6.