Fix running 'import run_isolated' at python interactive prompt.

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

Review URL:

git-svn-id: svn:// 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed