fix for #2014

The issue is due to disparity in incrementing the generator connect/reset count, resulting in the deletion of UVEs in redis on ttl expiry.
The generator connect count is updated when the Collector responds to the Control message from the generator (Generator::ReceiveSandeshCtrlMsg), whereas the reset count is updated when the connection request is not accepted by the Collector (Generator::DisconnectSession), resulting in reset count greater than the connect count. Collector refreshes the UVEs sent by the generator only if the connect count > reset count, resulting in the expiry of the UVEs in redis. Modified the code to increment the connect count on generator creation and Generator::ConnectSession instead of Generator::ReceiveSandeshCtrlMsg.