Remove some unused Python code

This patch removes code which is no longer used due to refactoring:

- http.InitSsl, last usage removed in commit 33231500 (“Convert RPC
  client to PycURL”)
- rapi.baserlib.MakeParamsDict, last usage remove in commit 4e5a68f8
  (“RAPI: rlib1 removal”)
- rapi.baserlib.ExtractField, last usage removed in commit 028c6b76
  (“RAPI:Fix root list and unittest for it.”)
- qa.qa_utils.AssertNotEqual, last real usage removed in commit
  2f4b4f78 (“Simplify QA commands”) (but it was still imported for a
  while, until we extended pylint to run over the QA code as well)
- qlang._IsHostname, added in commit f8638e28 (“Detect globbing
  patterns as query arguments”) but never used
- cmdlib._BuildNetworkHookEnvByObject, last usage removed in commit
  f22433c0 (“Locking related fixes for networks”)
- NLD constants, which are obsolete—the nbma project is no longer
  maintained and it's not working with current ganeti

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>