The current rate limiter disable logic won't trigger when the remote ip
is not forwarded, only when the remoteip plug is not enabled, which is
not the case on most instances since it's enabled by default. This
changes the behavior to warn and disable when the remote ip was not forwarded,
even if the RemoteIP plug is enabled.
Also closes #1620
When multiple requests are processed by rate limiter plug at the same
time and the bucket is not yet initialized, both would try to initialize
the bucket resulting in an internal server error.
