Tests/fix failing

Fixes failing tests when ran from inside vagrant. Hopefully this makes the tests happy on Travis after opening the pull request.

## Fixes

* `TestServer_globalRPCErrors` in `consul/server_test.go`

    Appears to need two servers since it checks for `remoteConsuls` to do a RPC call. If there aren't any it will return nil which previously made the test fail.

* Tests in `command/agent/agent_test.go`

    Were failing when trying to start up agents after a  shutdown. Turning the `Server` flag to `false` fixes these.
    Does this make sense or is they incorrectly passing with that change?
    Do the other tests in the agent test file need to have the `Server` flag set to true?
This test might actually have a timing issue if its failing on travis/vagrant. `remoteConsuls`, despite its name, contains the local instance as well as the remote ones. `globalRPC` should propagate an RPC call to all datacenters, including the local agent's datacenter. Launching the second server might be giving slower systems the extra milliseconds they need to complete the join and add the node to `remoteConsuls`. Maybe we can try wrapping this in a `waitForResult()` type test instead of adding the second server.