Bug 1698: Updated handling of choice node inside choice node

As it turned out, Composite Node to Binding codec
had problem with handling situations, where case
was augmented to choice and that case contained
another choice directly on first level.

Updated code to detect this situation and do proper lookup
to find choice in case in choice.

Change-Id: I2c39542520b842857884468dc0dcd28502ff41b3
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>
Merge "Bug 1698: Updated handling of choice node inside choice node"