Revert "gfs2: Use GL_NOBLOCK flag for non-blocking lookups"

Commit "gfs2: Use GL_NOBLOCK flag for non-blocking lookups" has several
issues, some of which are non-trivial to fix, so revert it for now:

  https://lore.kernel.org/gfs2/20240202050230.GA875515@ZenIV/T/

This reverts commit dd00aaeb

.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>