Merge branch 'stable-2.1'

* stable-2.1:
  Bump up version for 2.1.5 release
  RapiClient: fix multi-authentication in Python 2.6
  Remove rapi-user and rapi-pass from qa-sample.json
  qa: fix gnt-instance modify -t drbd
  qa: shutdown instance before trying disk convert
  Fix check in gnt-instance modify -t
  Document optional ctypes dependency
  Update NEWS for the 2.1.5 release
  Pass force variant option at instance creation
  BatchCreate: get force_variant from specs not opts
  BatchCreate: set a default for force_variant

Conflicts:
	INSTALL
	  - merge
	NEWS
	  - merge
	configure.ac
	  - keep 2.2 version
	lib/rapi/client.py
	  - keep curl version

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>