Raise max header size to accommodate large tokens

The max header is exceeded in the following scenario
- Auth tokens built with a keystone v3 API catalog
- A catalog with approximately 8 or more endpoints defined

Change-Id: Ie815e457c0b25ab828e780b5d90233ba0ceff61f
Closes-Bug: #1251026
Merge "Raise max header size to accommodate large tokens"