Always call 'spawn_after' for eventlet in fake mode.
Always call 'spawn_after' for eventlet in fake mode.

This commit changes the "eventlet_spawner" function used by fake mode
to always call eventlet.spawn_after, even when the time is zero.
The code had been recently changed to skip calling spawn_after, but it
turned out this changed the behavior of the API in fake mode.

Change-Id: Ic53c02b88a915893ada28e6765a18c2ed193df72
Fixes: bug #1084144

hplustree/trove,citrix-openstack/build-trove,mmasaki/trove,zhujzhuo/openstack-trove,cp16net/trove,denismakogon/trove-guestagent,denismakogon/trove-guestagent,mmasaki/trove,redhat-openstack/trove,hplustree/trove,zhangg/trove,citrix-openstack/build-trove,redhat-openstack/trove,openstack/trove,fabian4/trove,redhat-openstack/trove,zhangg/trove,changsimon/trove,fabian4/trove,changsimon/trove,citrix-openstack/build-trove,fabian4/trove,cp16net/trove,citrix-openstack-build/trove,zhujzhuo/openstack-trove,zhujzhuo/openstack-trove,changsimon/trove,openstack/trove,mmasaki/trove,citrix-openstack-build/trove,cp16net/trove,citrix-openstack-build/trove