Update version in tracks.yaml

newer bloom versions do not accept version strings other than x.y.z:
```
  File "/usr/bin/bloom-release", line 9, in <module>
    load_entry_point('bloom==0.5.9', 'console_scripts', 'bloom-release')()
  File "/usr/lib/pymodules/python2.7/bloom/commands/release.py", line 1001, in main
    args.pull_request_only)
  File "/usr/lib/pymodules/python2.7/bloom/commands/release.py", line 897, in perform_release
    tracks_dict = get_tracks_dict_raw()
  File "/usr/lib/pymodules/python2.7/bloom/config.py", line 270, in get_tracks_dict_raw
    validate_track_versions(tracks_dict)
  File "/usr/lib/pymodules/python2.7/bloom/config.py", line 254, in validate_track_versions
    .format(track['version']))
ValueError: Invalid version 'v2.7.0-rc1', it must be formatted as 'MAJOR.MINOR.PATCH'
```