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

An equivalent fix will be required for all projects which use
eventlet.wsgi.

Closes-Bug: #1190149

Change-Id: Ia0882e43395f1025137173b51aab147433b54255
Merge "Raise max header size to accommodate large tokens"