Description of problem:
When there are 2 Middleware Providers, each of them has Domain Mode EAP7 server, the servers of first provider's Server Groups are shown under second provider's Server Group. So one has all, second has nothing.

Version-Release number of selected component (if applicable):
DR2

How reproducible:
always

Steps to Reproduce:
1. Register the first Middleware Provider into CFME.
2. On separate VM, manually start a Domain mode EAP7 server with agent enabled and connected to the first Middleware Provider.
3. On another separate VM, manually start EAP7 image in Domain mode with the Hawkular agent pre-installed. As described in Quickstart Guide.
4. Referesh both providers relationships in UI operation.
5. Go To Middleware -> Providers.
6. Select the first provider, go to Domains -> select the Domain -> go to Server Groups -> select one of Server groups (i.e. main-server-group) -> go to Servers.
You will find all servers from both providers belonging to main-server-group here.
7. Do the same for other-server-group.
You will find all servers from both providers belonging to other-server-group here.
8. Do the same for the second provider.
You will find servers list for both server groups empty.

Actual results:
all servers from server groups of both providers are shown under one provider's server group.

Expected results:
should shown under appropriate server group

Additional info:
Servers are listed correctly directly under each provider.

In DB, I can see wrong "server_group_id" for servers in middleware_servers table.