Previously the in-process functional test setup attempted to insert
etag-quoter in the proxy pipeline by replacing the substring 'cache
listing_formats' with 'cache etag-quoter listing_formats'. However,
the pipeline had already been modified to have 'cache domain-remap
listing_formats', so the etag-quoter replacement failed silently.
This patch modifies the etag-quoter replacement to match just
'cache'. Some helper functions are also introduced to make the
pipeline modification more uniform and to consistently verify the
intended modifications have been achieved, or otherwise raise an
exception.
Change-Id: I640837a4da985bcbe48f9ae5eeb56385b11034eb
86081b7822