remove keystonemiddleware settings from api-paste.ini

They can/should be set in the trove.conf instead, to
centralize all user-preserved/editable changes in the main
configuration file, and allow the ability to track api-paste.ini
unmodified from master.

Change-Id: I9eae06f564c4f99255fc627dbd26006d9048be46
Merge "remove keystonemiddleware settings from api-paste.ini"