fix Singleton.__call__ error

fix Singleton.__call__ error
Merge pull request #344 from bentenshan/patch-1

fix Singleton.__call__ error
Fixing Node.monitor() to read entire prompt marker.

Applying @cdburkard fix to #322
updaing build.py to use 12.04.5 and extract kernel using noload
Merge branch 'master' of github.com:mininet/mininet