ext4: don't try to clear the orphan_present feature block device is r/o

When the file system is frozen in preparation for taking an LVM
snapshot, the journal is checkpointed and if the orphan_file feature
is enabled, and the orphan file is empty, we clear the orphan_present
feature flag.  But if there are pending inodes that need to be removed
the orphan_present feature flag can't be cleared.

The problem comes if the block device is read-only.  In that case, we
can't process the orphan inode list, so it is skipped in
ext4_orphan_cleanup().  But then in ext4_mark_recovery_complete(),
this results in the ext4 error "Orphan file not empty on read-only fs"
firing and the file system mount is aborted.

Fix this by clearing the needs_recovery flag in the block device is
read-only.  We do this after the call to ext4_load_and_init-journal()
since there are some error checks need to be done in case the journal
needs to be replayed and the block device is read-only, or if the
block device containing the externa journal is read-only, etc.

Cc: stable@kernel.org
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1108271


Cc: stable@vger.kernel.org
Fixes: 02f310fc ("ext4: Speedup ext4 orphan inode handling")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>