xfs_db: fix inode CRC validity state, and warn on read if invalid

xfs_db: fix inode CRC validity state, and warn on read if invalid

Currently, the "ino_crc_ok" field on the io cursor reflects
overall inode validity, not CRC correctness.  Because it is
only used when printing CRC validity, change it to reflect
only that state - and update it whenever we re-write the
inode (thus updating the CRC).

In addition, when reading an inode, warn if the CRC is bad.

Note, when specifying an inode which doesn't actually exist,
this will claim corruption; I'm not sure if that's good or
bad. Today, it already issues corruption errors on the way;
this adds a new message as well:

xfs_db> inode 129
Metadata corruption detected at block 0x80/0x2000
Metadata corruption detected at block 0x80/0x2000
...
Metadata CRC error detected for ino 129

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>