[openib-general] Failed multicast join with new multicast module

[Sean Hefty]

Hal Rosenstock wrote:
> Send-only joins is another case. These are full member joins (JoinState
> 1) to groups which are not yet created so they fail.

I see the problem, and checked in a fix.  I forgot to record the last join 
operation that was initiated, so that it could be failed on an error.  This 
resulted in the join being retried repeatedly.  The join request should now 
fail, and ipoib will retry using an exponential backoff strategy.

- Sean