pimd: skip init of mlag roles based on the zebra capabilities message

pimd: skip init of mlag roles based on the zebra capabilities message

Looks like the cap setting was added for testing mlag via zebra test cli
to config the mlag role. However it is interfering with the valid state
updates rxed from the MLAG daemon based on timing (in some cases the
MLAG state changes are rxed before the capabilities).

Reference logs -
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
root@TORC11:mgmt:/home/cumulus# grep -ri "my_role\|MlagRole" /var/log/frr/bgpd.log
2021/06/18 13:26:40.380130 PIM: pim_mlag_process_mlagd_state_change: msg dump: my_role: SECONDARY, peer_state: DOWN
2021/06/18 13:26:40.380766 PIM: pim_mlag_process_mlagd_state_change: msg dump: my_role: SECONDARY, peer_state: DOWN
2021/06/18 13:26:41.382258 PIM: pim_mlag_process_mlagd_state_change: msg dump: my_role: SECONDARY, peer_state: RUNNING
2021/06/18 13:26:41.382379 PIM: pim_mlag_process_mlagd_state_change: msg dump: my_role: PRIMARY, peer_state: RUNNING
2021/06/18 13:26:52.386071 ZEBRA: Sending capabilities to client pim: MPLS enabled numMultipath 128 GR disabled MaintMode off MlagRole 0
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Ticket: #2691629

Signed-off-by: Anuradha Karuppiah <anuradhak@nvidia.com>