Fix running 'import run_isolated' at python interactive prompt.

This was breaking 'import swarming' since it imports run_isolated.

swarming.py:
- Rename manifest_hash to isolated_hash, the previous name was confusing.
- Only add the data section if necessary, if .zip_and_upload() was called.
- Assumes slave_os is already the proper key in PLATFORM_MAPPING_SWARMING.
- Have polling quit sooner.

R=vadimsh@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/25549003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/swarm_client@226272 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed