Nuke EC2 API service in defaults

Tempest does not test EC2 by default anymore:
Ib5e24e19bcba9808a9f49fe7f328668df77fe4f9

So we don't need to run nova ec2 API service by default.

Change-Id: Ieec0ca1361baf0978d96e69e1134f699c1af3bb9
diff --git a/stackrc b/stackrc
index f949ccb..edf23ce 100644
--- a/stackrc
+++ b/stackrc
@@ -91,7 +91,7 @@
 ENABLE_HTTPD_MOD_WSGI_SERVICES=True
 
 # Set the default Nova APIs to enable
-NOVA_ENABLED_APIS=ec2,osapi_compute,metadata
+NOVA_ENABLED_APIS=osapi_compute,metadata
 
 # Set the root URL for Horizon
 HORIZON_APACHE_ROOT="/dashboard"