Remove rabbit_notifier (Sync notifier with oslo d6e1ba7)

Remove rabbit_notifier (Sync notifier with oslo d6e1ba7)

rpc_notifier is available since grizzly, and rabbit_notifier
was printing deprecation messages since then. Remove it
for icehouse. This includes a sync to oslo-incubator, which
includes the following commits:

  aff0171 Remove "vim: tabstop=4 shiftwidth=4 softtabstop=4" from headers
  8575d87 Removed copyright from empty files
  8b2b0b7 Use hacking import_exceptions for gettextutils._
  6fa29ae Trivial: Make vertical white space after license header
          consistent
  d7ae4ff Remove deprecated Grizzly features

DocImpact: Remove all references to rabbit_notifier and replace
it with rpc_notifier.

Change-Id: I889b43dfcebe6574dfa00ea50818f85732860d98