ocfs2: Add an incompat feature flag OCFS2_FEATURE_INCOMPAT_CLUSTERINFO

OCFS2_FEATURE_INCOMPAT_CLUSTERINFO allows us to use sb->s_cluster_info for
both userspace and o2cb cluster stacks. It also allows us to extend cluster
info to include stack flags.

This patch also adds stackflags to sb->s_clusterinfo. It also introduces a
clusterinfo flag OCFS2_CLUSTER_O2CB_GLOBAL_HEARTBEAT to denote the enabled
global heartbeat mode.

This incompat flag can be set/cleared using tunefs.ocfs2 --fs-features. The
clusterinfo flag is set/cleared using tunefs.ocfs2 --update-cluster-stack.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index fa1be1b..7554317 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -2149,7 +2149,9 @@
 		goto bail;
 	}
 
-	if (ocfs2_userspace_stack(osb)) {
+	if (ocfs2_clusterinfo_valid(osb)) {
+		osb->osb_stackflags =
+			OCFS2_RAW_SB(di)->s_cluster_info.ci_stackflags;
 		memcpy(osb->osb_cluster_stack,
 		       OCFS2_RAW_SB(di)->s_cluster_info.ci_stack,
 		       OCFS2_STACK_LABEL_LEN);