Fix race in NoOpTestPeerProxy and remove unused field
Fix race in NoOpTestPeerProxy and remove unused field

This fixes a race in NoOpTestPeerProxy by adding a lock as
its fields may potentially be accessed by multiple threads.

This also simplifies the flow a bit and removes an unused
field.

Change-Id: I38b05864e327384970dc3f75ccfbba709f42fa02
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4865
Tested-by: jenkins
Reviewed-by: Todd Lipcon <2c763d726a8c2f6afda9be7e0e56a2caa6bb5e6b@cloudera.com>

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