AAH: Fix a bug in the master election state machine.

Client's of Masters who disappear before the client has processed even
one timesync response should not enter the Ronin state.  Since they
have never synced to the old Master's timeline, by becoming Ronin they
run the risk of defeating other new Ronin's in the master election,
even though they don't have any idea what time it is on the old
Master's timeline and therefore are unsuitable to serve as the new
Master.  Instead, they should transition to the Initial state, where
other new Ronins (who do know what time it is) have the chance to step
in and serve as master of the old timeline.  If there are no other
Ronin who can do the job, then the old timeline is dead and by
transitioning to Initial, a new one will be generated.

Change-Id: Iaa95313bfe68a971be2764e252ebf4b34313013d
Signed-off-by: John Grossman <johngro@google.com>

services/aah_timesrv/aah_timesrv.cpp

@@ -1016,9 +1016,21 @@ bool AAHTimeService::becomeMaster() {
 }
 
 bool AAHTimeService::becomeRonin() {
-    mRonin_WhoIsMasterRequestTimeouts = 0;
-    setState(STATE_RONIN);
-    return sendWhoIsMasterRequest();
+    // If we were the client of a given timeline, but had never received even a
+    // single time sync packet, then we transition back to Initial instead of
+    // Ronin.  If we transition to Ronin and end up becoming the new Master, we
+    // will be unable to service requests for other clients because we never
+    // actually knew what time it was.  By going to initial, we ensure that
+    // other clients who know what time it is, but would lose master arbitration
+    // in the Ronin case, will step up and become the proper new master of the
+    // old timeline.
+    if (mCommonClock.isValid()) {
+        mRonin_WhoIsMasterRequestTimeouts = 0;
+        setState(STATE_RONIN);
+        return sendWhoIsMasterRequest();
+    } else {
+        return becomeInitial();
+    }
 }
 
 bool AAHTimeService::becomeWaitForElection() {