Fixed spec/requests/ authentication specs

- Update session_store to use :memory instead of default cookie_store for tests, eliminating the 4K limit that was giving us the 500's.
- Needed to specify HTTP_USER_AGENT for a couple of tests in auth_spec.rb

This fix is needed before enabling spec:requests as part of test:vmdb for the REST API.

@martinpovolny @Fryguy please review.

Also what are we putting in there that could possibly hit 4k?
 On Nov 24, 2014 7:20 PM, "Jason Frey" <fryguydev@gmail.com> wrote:

> But the default is not cookie store, it's memcache...I'm confused.
>  On Nov 24, 2014 7:09 PM, "Alberto Bellotti" <notifications@github.com>
> wrote:
>
>> In vmdb/config/initializers/session_store.rb:
>>
>> > @@ -1,4 +1,6 @@
>> > -if MiqEnvironment::Process.is_web_server_worker?
>> > +if !MiqEnvironment::Process.is_web_server_worker?
>> > +  Vmdb::Application.config.session_store :memory_store if Rails.env.test?
>> > +else
>>
>> we were getting 500's with the default 4k limit with cookie_store, ye-old
>> CookieOverflow errors.
>>
>> —
>> Reply to this email directly or view it on GitHub
>> <https://github.com/ManageIQ/manageiq/pull/1116/files#r20833676>.
>>
>