Revert "gfs2: read journal in large chunks to locate the head"

This reverts commit 2a5f14f2

.

This patch causes xfstests generic/311 to fail. Reverting this for
now until we have a proper fix.

Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>