xfs_db: Don't ASSERT on unrecognized metadata

xfs_db: Don't ASSERT on unrecognized metadata

For some types, (for example attr3) if the metadata is not recognized
as the requested type, we can hit an ASSERT when trying to print
the type:

xfs_db: print.c:164: print_flist_1: Assertion `fa->arg & 64' failed.
Aborted (core dumped)

This can happen for corrupted metadata or even just a misdirected
user command; there's no reason to ASSERT.  If we get here, print
something helpful and carry on.

[sandeen: write the commit log]

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>