Improving tests to fix testBindNormalWidget_withoutConfig, and beyond

1. Make waitXXX methods fail if the condition diesn’t turn true.
2. Waiting for loading to complete in tearDown instead of reloading the
 model
3. Avoiding waiting for load-complete where loading didn’t start
4. Disabling last test in AddConfigWidgetTest
5. Waiting for loading to complete inside setupAndVerifyContents(), not
 outside
6. Unifying how we wait for loader to complete
7. Adding more logging

Bug: 117332845
Test: running all Nexus tests
Change-Id: I3070e1ac2b9161179cc3e0800b0cd8162807389a