And fix the 'value not used' issues.
Many of these are not bugs, but a few are tests not checking errors, and
one appears to be a missed error in non-test code.
* Add function to wait for serfHealth in api tests
* Disable connect when creating semaphore test clients
* Wait for serfHealth when creating sessions in their tests
* Add helper functions to create lock/semaphore sessions without checks
* Log passing tests to prevent timeout in Travis due to lack of output
This is necessary as consul-api's tests require a real consul instance
to be running. We can't directly import an agent to fire up an instance,
due to the way this would create an import cycle. These tests instead
will start a consul instance using the binary in $PATH (if it exists).
