[Service Plans UI] Remove Tenant button is enabled even when tenants are not selected. Tenants and Backends that are already added to the Service plan are still populated in the Add Tenant and Add Backend dropdowns.

[PravinRanjan10]

Issue/Feature Description:

Why this issue to fixed / feature is needed(give scenarios or use cases):

How to reproduce, in case of a bug:

Other Notes / Environment Information: (Please give the env information, log link or any useful information for this issue)

• While adding tenants in SSP, only those tenants should be displayed..which are already not added. But here it is listing all tenants(already added also)
  

• The same above issue persist for adding backends also.

• Remove tenants button getting active even without selected any tenats.
  How to recreate:

1. Add two tenants
2. Remove any one
3. Now, Remove buttons will be active, and able to click on remove without selecting button..and later it fails.
   

• There is no tenants, but still remove button is active for removing.