[pkg/vm_service] fix to analysis warnings about required arguments

Change-Id: I752d0d09b9cee234fe9e8c06144f210eb9a5bb55
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/162401
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Devon Carew <devoncarew@google.com>

pkg/vm_service/test/server_test.dart

@@ -57,6 +57,7 @@ void main() {
         ),
         libraries: [],
         breakpoints: [],
+        isSystemIsolate: false,
       );
       var request = rpcRequest("getIsolate", params: {'isolateId': isolate.id});
       when(serviceMock.getIsolate(isolate.id))
@@ -84,6 +85,7 @@ void main() {
         ),
         libraries: [],
         breakpoints: [],
+        isSystemIsolate: false,
       );
       var request = rpcRequest("setVMTimelineFlags", params: {
         'isolateId': isolate.id,