Fix conference call duration issue

The conf call start time is updated with a delay resulting
in abnormal display of the conf call duration.
Fixed by updating the duration only when the call start
time is non-zero.

Change-Id: I6a1b6c0ab0021d6e6e260bf1743487ec364366c4
Signed-off-by: Narendra <nagarw@codeaurora.org>
diff --git a/InCallUI/src/com/android/incallui/CallCardPresenter.java b/InCallUI/src/com/android/incallui/CallCardPresenter.java
index 10bf5e6..76dd849 100644
--- a/InCallUI/src/com/android/incallui/CallCardPresenter.java
+++ b/InCallUI/src/com/android/incallui/CallCardPresenter.java
@@ -541,8 +541,10 @@
             mCallTimer.cancel();
         } else {
             final long callStart = mPrimary.getConnectTimeMillis();
-            final long duration = System.currentTimeMillis() - callStart;
-            ui.setPrimaryCallElapsedTime(true, duration);
+            if (callStart > 0) {
+                final long duration = System.currentTimeMillis() - callStart;
+                ui.setPrimaryCallElapsedTime(true, duration);
+            }
         }
     }