BUG-1281: make methods static

As it turns out ControllerContext has a few methods which do not touch
instance state -- make those static and fixup callers.

Change-Id: Id8d04f2426435528ee754f56b34f91d25a49d3ee
Signed-off-by: Robert Varga <rovarga@cisco.com>
BUG-1281: eliminate thread-unsafe lookup

The URI/name lookup map was not safe when context was reloaded. Get rid
of it for now, as SchemaContext can maintain reasonably-fast lookups. At
the same time make sure we share codepaths as much as possible.

Change-Id: If78d8143e94446fe9b38da894611b1c8b61f57f3
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge changes If78d8143,Id8d04f24

* changes:
  BUG-1281: eliminate thread-unsafe lookup
  BUG-1281: make methods static