gfs2: Remove DLM_LKF_ALTCW / DLM_LKF_ALTPR code

Commit 6802e340 ("[GFS2] Clean up the glock core") stopped passing
the LM_FLAG_ANY flag down to gdlm_lock() (then gfs2_lm_lock()).  Since
then, gfs2 effectively hasn't been using dlm's DLM_LKF_ALTCW /
DLM_LKF_ALTPR flags, but the code still suggests that it does.  Recent
testing shows that those flags don't even work reliably anymore, so
instead of fixing code that hasn't been used since 2008, remove it.

In addition, clean up how the flags are passed to [gd]lm_lock().

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Andrew Price <anprice@redhat.com>