Make test-apt-download-progress less flaky

Make test-apt-download-progress less flaky

The test is a bit flaky. In order to get it less flaky, reduce
the speed in each run. To compensate for issues, start with a
higher speed level. Also increase the number of runs to 10.

Furthermore, http get the same multiple-run loop, and the log
files are changed to indicate the protocol being tested, as it's
not obvious which one fails if it fails in quiet mode.

Gbp-Dch: ignore