fix(lock): handle errors on etcd initialization
fix(lock): s/sempahore/semaphore
fix(updateengine): set error appropriately from dbus call
Merge pull request #6 from jonboulle/typos

fix(lock): s/sempahore/semaphore
Merge pull request #8 from jonboulle/err-fix

fix(updateengine): set error appropriately from dbus call
Merge pull request #5 from jonboulle/master

fix(lock): handle errors on etcd initialization
fix(lock): fix bug and improve semaphore test coverage

Calling Unlock() on a Lock that did not hold the semaphore would panic
when the semaphore had >0 (other) holders.
Added test coverage for all Semaphore actions.