Fix incorrect BGP entity name & type pairs

Fix incorrect BGP entity name & type pairs

Get_Owner_And_Successors_For_device requires Bgpcep as the entity type
when the BGP RIB name is given as the entity name.
Another option is to use the entity name with the '-service-group'
suffix, e.g. 'example-bgp-rib-service-group' instead of
'example-bgp-rib', with 'org.opendaylight.mdsal.ServiceEntityType'
as the entity type. In this case the initial attempt to get
the ownership information from
Get_Owner_And_Candidates_For_Device_Singleton will
fail and Get_Owner_And_Candidates_For_Device_Rpc will be used
as a fallback.

There are several test cases that incorrecly use the BGP RIB name with
'org.opendaylight.mdsal.ServiceEntityType'. Fix the errors with the
first option (use 'Bgpcep' as the type) to utilize the abstraction
provided by the keyword.

Signed-off-by: Sangwook Ha <sangwook.ha@verizon.com>
Change-Id: Ic44cd0f35531cc22bc3e4627ba2edec56084e075