Make apex.updatable default to true.

Update tests accordingly and add a new test case for this.

Bug: 180375550
Test: Treehugger
Change-Id: I835e189f4dae1e4bc79dce7bc59b7b9c7bd19fd9

sdk/java_sdk_test.go

@@ -211,6 +211,7 @@ func TestBasicSdkWithJavaLibrary(t *testing.T) {
 			uses_sdks: ["mysdk@1"],
 			key: "myapex.key",
 			certificate: ":myapex.cert",
+			updatable: false,
 		}
 
 		apex {
@@ -219,6 +220,7 @@ func TestBasicSdkWithJavaLibrary(t *testing.T) {
 			uses_sdks: ["mysdk@2"],
 			key: "myapex.key",
 			certificate: ":myapex.cert",
+			updatable: false,
 		}
 	`)