scanner: tag the correct gflag as hidden
scanner: tag the correct gflag as hidden

The intent of commit 125bc152 was to tag the new gflag being added as
hidden, not the existing one.

Change-Id: I55eb012c782950b86c494d9a4f8c0e9af13a315d
Reviewed-on: http://gerrit.cloudera.org:8080/2526
Reviewed-by: Todd Lipcon <2c763d726a8c2f6afda9be7e0e56a2caa6bb5e6b@apache.org>
Tested-by: Kudu Jenkins

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