Configuration changes required to support VMware NSX plugin

(Formerly known as Nicira NVP plugin).

Following Neutron change 79fbeb7ebebc0dfbe143aee96fbc250d1b9e7582,
this patch introduces the new naming scheme for Neutron VMware NSX
plugin configuration.

Related-blueprint: nvp-third-part-support (aka bp vmware-nsx-third-party)
Partial-implements blueprint: nicira-plugin-renaming

Change-Id: If7790887661507bfdec6d2b97c0f99609039aa73
Correct Qpid package name in files/apts/neutron

Ubuntu qpid server package is named as "qpidd", but
files/apts/neutron has an entry "qpid".

Change-Id: Ie3f8391a7404bdeb222acfcce77ca80a14ea8693
Closes-Bug: #1267459
Robustify service shutdown

* Save PID when using screen in screen_it()
* Add screen_stop()
* Call out service stop_*() in unstack.sh functions so screen_stop()
  can do its thing

Closes-bug: 1183449
Change-Id: Iac84231cfda960c4197de5b6e8ba6eb19225169a
Merge "Correct Qpid package name in files/apts/neutron"
Merge "Robustify service shutdown"
Merge "Configuration changes required to support VMware NSX plugin"