Fixed scheduler driver to call disconnected() when master fails over.

Review: https://reviews.apache.org/r/11191
Fixed master to send a FrameworkReregistered message when the
framework re-registers with a failed over master.

Review: https://reviews.apache.org/r/11348
Fixed release script to use git instead of svn.

Review: https://reviews.apache.org/r/11381
Fixed a bug in the release script regarding tag creation.