Fixes admin session cookie test

- Currently the test is taking the response date
which is in UTC and passes it through moment()
which by default parses input as local time.  We
then add 12 hours to this now local time
and when compared against the response set-cookie
header the time spread is wrong.

- To fix we’re parsing the response date with
moment.utc which parses the date in UTC.
Merge pull request #1816 from hswolff/fix-admin-session-test

Fixes admin session cookie test