Search test_result.xml in the CTS report zipfile

parse_cts_report assumed a fixed path to test_result.xml
in the CTS report zipfile. This cl removed this assumption
by searching all files in the zipfile, and returning
success if there is exact one match.

Bug: 293809772
Test: ./compare_cts_reports.py -r report_zip_1 \
        -r report_zip_2 --mode 2 --output-dir output
Change-Id: I6e82749a4aea11c5aa6e7d514dd538bd0cae0cad
2 files changed