Android: removes old "keep_test_server_ports".

This option is no longer in use, clean it up.

BUG=

Review URL: https://codereview.chromium.org/68263025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236533 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236533