Fix TestRaft_StartAsLeader

[schristoff]

TestRaft_StartAsLeader and TestRaft_SingleNode are similar however a key difference is StartAsLeader uses the "StartAsLeader" configuration flag which through testing we are finding is causing multiple failures.
We will continue to dig in to see if this configuration flag is necessary, and if not we can "fix" this test by removing the flag.

[schristoff]

Relevant Issue: #372
The backstory behind the flag is that we wanted nodes to not "elect" themselves as leaders but just start as a leader so that starting up a -dev mode type of cluster or running tests could be faster.

[langmartin]

This looks good to me. Since StartAsLeader was part of our public interface and at least one downstream project used it, should we leave it in the config file and have it log a warning instead of doing anything?

[langmartin]

Thinking and talking about it: I think this is fine, and we should just add a line in the Changelog to document removing the config field