On recovery fail, do rm -rf /tmp/mesos/meta.
Fixed handling of executor history on slaves.

The list of retired (completed) frameworks is now a stout cache rather
than a boost circular buffer.  There are now key iterator accessors for
the cache class, and a removal member.

This resolves https://issues.apache.org/jira/browse/MESOS-616.

Review: https://reviews.apache.org/r/13401