Make _build_uri_path output predictable

This is done by ensuring that filters are
serialized in their alphabetical order.

Tweak tests affected by this.

This is done in the context as defined by
etherpad: neutron-random-hashseed

Partial-bug: #1348818

Change-Id: Ibe79716a340195ca0365f276ef6e3e728f1a94a1
Merge "Make _build_uri_path output predictable"