Fixed a potential use after free bug.
Fixed a potential use after free bug.

Moving a framework to `frameworks.completed` transfers ownership of the
Framework to that container and e.g., using the original framework
pointer after that could fail (the framework could e.g., be already be
rotated out).

This patch fixes the master to not use the potentially cleaned up
framework pointer anymore.

Review: https://reviews.apache.org/r/71781/

Gilbert88/mesos,kaysoky/mesos,Gilbert88/mesos,dforsyth/mesos,abudnik/mesos,dforsyth/mesos,Gilbert88/mesos,abudnik/mesos,dforsyth/mesos,dforsyth/mesos,abudnik/mesos,reneploetz/mesos,Gilbert88/mesos,abudnik/mesos,reneploetz/mesos,abudnik/mesos,reneploetz/mesos,reneploetz/mesos,Gilbert88/mesos,kaysoky/mesos,kaysoky/mesos,dforsyth/mesos,kaysoky/mesos,dforsyth/mesos,Gilbert88/mesos,Gilbert88/mesos,reneploetz/mesos,kaysoky/mesos,reneploetz/mesos,abudnik/mesos,dforsyth/mesos,kaysoky/mesos,abudnik/mesos,kaysoky/mesos,reneploetz/mesos