Router create distributed accepts lower case

Neutron router-create optional argument distributed
does not accept "true/false" anymore.
It only accepts value with Camel case "True/False".

This patch will allow the users to provide both
True/true or False/false.

Change-Id: I79577bd70a796543b9dea53b4839512eb8944d7c
Closes-bug: #1368934
Merge "Router create distributed accepts lower case"