Added cached_cocuments property to XCAPManager

Ignore-this: baab6079ac3ebe16c2d35fa78bbb1b03

darcs-hash:20100917090027-56b4d-0467c2ca0c7e6420f9817366dd6c05c334621061
Don't wait for pending operations to finish on shutdown

Ignore-this: 9d56d048597d2ec7eaba922c10abfa2b

There is no need to wait for a registration/subscription if
we are shutting down

darcs-hash:20100917172526-56b4d-188a287f9a9c16b37416bb24928d11f3876a992f