In cases when 2 generator connects are received, we disconnect
both sessions by enqueueing close on the existing sandesh session
from the state machine of the new sandesh session. In this
case, ensure that the sandesh session connection and state
machine are accessed via mutex to prevent a concurrent delete
of the sandesh session.
Remove mutex_ from sandesh state machine
Merge pull request #38 from Juniper/meghb_2773

In cases when 2 generator connects are received, we disconnect