Factorize custom asserts.

Also a few utilities that were in the way, and some opportunistic
cleanups.

Test: FrameworksNetTest NetworkStackTest
Change-Id: I385070e2044fd967cb18f1ffea9a86a4627b742e
diff --git a/tests/net/common/Android.bp b/tests/net/common/Android.bp
index db1ccb4..e44d460 100644
--- a/tests/net/common/Android.bp
+++ b/tests/net/common/Android.bp
@@ -21,12 +21,12 @@
     srcs: ["java/**/*.java", "java/**/*.kt"],
     static_libs: [
         "androidx.test.rules",
-        "frameworks-net-testutils",
         "junit",
         "mockito-target-minus-junit4",
+        "net-tests-utils",
         "platform-test-annotations",
     ],
     libs: [
         "android.test.base.stubs",
     ],
-}
\ No newline at end of file
+}