gfs2: Partially revert gfs2_inode_lookup change

Commit c412a97c changed delete_work_func() to always perform an
inode lookup when gfs2_try_evict() fails.  This doesn't make sense as a
gfs2_try_evict() failure indicates that the inode is likely still in
use.  Revert that change.

Fixes: c412a97c ("gfs2: Use TRY lock in gfs2_inode_lookup for UNLINKED inodes")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>