GFS2: Dump better debug info if a bitmap inconsistency is detected

On rare occasions we encounter gfs2 problems where an
invalid bitmap state transition is attempted.  For example,
trying to "unlink" a free block.  In these cases, there
is really no useful information logged to debug the problem.
This patch adds more debug details that should allow us to
more closely examine the problem and possibly solve it.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>