We encountered bug 2037312 in unit tests when attempting to get this
change rolled out. Heat apparently will attempt to set is_admin using
policy logic if it's not passed in for a new context; this breaks as the
context we are requested doesn't have all the needed information to
exercise the policy logic.
is_admin is just a bool; it's not sensitive; easiest route forward is to
add it to the safe list
Closes-bug: 2037312
Change-Id: I78b08edfcb8115cddd7de9c6c788c0a57c8218a8
(cherry picked from commit c1b606f77e69a2829fcfdb74b8b3f646d4b60929)
(cherry picked from commit 29623702fc1ebce240b6d368ee95ab9f479d5e02)
45a0141468