Android: map the forwarded ports at the host driven level.

Rather than (un)mapping the ports on each one of the internal instrumentation
tests, do it higher up at the host driven level.
Ensure the test server is fully setup and tear down.
Ensure the adb port is fully unmapped at the host forwarder level. 
Add more log information to the forwarder, and add them to TestResult.log in case of failure.
Kill the device forwarder when unmapping all ports.


BUG=313809

Review URL: https://codereview.chromium.org/59313003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234486 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234486