core: Disable panic mode

It is now discovering legitimate errors in some tests that need to be
resolved first. Follow progress at #3293.

core/src/main/java/io/grpc/internal/ManagedChannelImpl.java

@@ -119,7 +119,11 @@ final class ManagedChannelImpl extends ManagedChannel implements Instrumented<Ch
       @Override
       void handleUncaughtThrowable(Throwable t) {
         super.handleUncaughtThrowable(t);
-        panic(t);
+        // Disabled because it breaks some tests, as it detects pre-existing issues.
+        // See #3293
+        if (false) {
+          panic(t);
+        }
       }
     };
 

core/src/test/java/io/grpc/internal/ManagedChannelImplTest.java

@@ -97,6 +97,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 import javax.annotation.Nullable;
 import org.junit.After;
+import org.junit.Assume;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -1673,6 +1674,8 @@ public class ManagedChannelImplTest {
   }
 
   private void verifyPanicMode(Throwable cause) {
+    Assume.assumeTrue("Panic mode disabled to resolve issues with some tests. See #3293", false);
+
     @SuppressWarnings("unchecked")
     ClientCall.Listener<Integer> mockListener =
         (ClientCall.Listener<Integer>) mock(ClientCall.Listener.class);