Minor comment clarifications for alter schema
Minor comment clarifications for alter schema

PONR -> point of no return, numbering fix, etc.

Change-Id: Ie9c1b7c19eaffe80457f982b1e9c7c68293e9243
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1441
Tested-by: jenkins
Reviewed-by: Todd Lipcon <2c763d726a8c2f6afda9be7e0e56a2caa6bb5e6b@cloudera.com>

helifu/kudu,cloudera/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,InspurUSA/kudu,andrwng/kudu,InspurUSA/kudu,cloudera/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,andrwng/kudu,andrwng/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,cloudera/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,andrwng/kudu,helifu/kudu,cloudera/kudu,cloudera/kudu,cloudera/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,andrwng/kudu,helifu/kudu,EvilMcJerkface/kudu,andrwng/kudu,andrwng/kudu,helifu/kudu,cloudera/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,cloudera/kudu,cloudera/kudu,andrwng/kudu,InspurUSA/kudu,InspurUSA/kudu,andrwng/kudu,InspurUSA/kudu,helifu/kudu