started servers test
cafe AS client delete_server implemented
force delete a group on fixture cleanup
ScalingPolicyFixture passes extra args to GroupFixture
Delete server tests implemented
using server id from wait_for_exp_active_servers
create_policy uses sp_change param
new group for each test

by using setUp() instead of setupClass()
not using 'or' operator - thanks @cyli

since it does not allow 0 value
better docstring - thanks @lvh

since it makes replace args clearer
better docstring - per @kivattik
Choose second server to delete - thanks @kivattik
test to delete server in another group - thanks @kivattik
Merge pull request #652 from rackerlabs/as-274-server-delete-qe

AS-274: DELETE groups/<groupId>/servers/<serverId> tests (merged from amtrak)