Fixed Validity element in common-policy XML payload

Ignore-this: 720b984c22b28592fcdd953706e13f7b

darcs-hash:20100121131259-1e3d8-5c4ae8f70da0121d9648c006fd3fe12e945d731d
Modified Engine to not block in stop method

Ignore-this: eefc77fa76e20bfd86518160f3f50685

darcs-hash:20100121135950-1e3d8-d9a2ac9ca9b26062ffb4b81d221bc6a4c3fb8134