Make generates manifests for modules that are missing AndroidManifest.xml
files in order to paper over differences between aapt and aapt2. These
manifests don't have an <application> tag. which was tripping up an
unexercised error path in manifest_check.py.
Change manifest_check,py's extract_uses_libs_xml to consider manifests
with no application tag as having empty uses_library and
optional_uses_library lists. Also fix up a few nearby pylint warnings.
Fixes: 303554426
Test: m ConnectivityMonitorRobotests
Change-Id: I3815a1c86e24d7b3dea7f4ea26c34d3af182ded1