xfs: allow inode inactivation during a ro mount log recovery

In the next patch, we're going to prohibit log recovery if the primary
superblock contains an unrecognized rocompat feature bit even on
readonly mounts.  This requires removing all the code in the log
mounting process that temporarily disables the readonly state.

Unfortunately, inode inactivation disables itself on readonly mounts.
Clearing the iunlinked lists after log recovery needs inactivation to
run to free the unreferenced inodes, which (AFAICT) is the only reason
why log mounting plays games with the readonly state in the first place.

Therefore, change the inactivation predicates to allow inactivation
during log recovery of a readonly mount.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>