logtags: Support # line comments.

Allow # line comments to start anywhere in a line, not just in column 0.

Test: Added trailing # comments to SecurityLogTags.logtags and checked
      that 'make droid' still worked.
Test: Piped a few example lines through a small test script to verify
      that the following line behaved as expected:
      line = re.sub('#.*$', '', line)

Change-Id: Ib7904620adf8da7d11511ef6d8300e5fb4c73c29