gfapi: fix mem-types initialisation

... and also fill the body of mem_acct_init().

Change-Id: I457d0629c20f999dd2f50e710c75b1c7575b6c19
BUG: 1021904
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/6134
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>