Remove configuration parameter EXTRA_OPTS

According to the comments in stack.sh the configuration parameter
EXTRA_OPTS should be removed during the Juno cycle.

Change-Id: Ic71d38d6f9b8a8949e45ce3321d593ee2f8feb40
Merge "Remove configuration parameter EXTRA_OPTS"
Merge commit 'refs/changes/83/86083/2' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch