This is a consolidation effort, avoiding usage
of naked strings in codebase. Whenever possible
use constants which can be repurposed elsewhere.
This also fixes `goconst ./...` reported issues.
* Rename GenericArgs to AuthRPCArgs
* Rename GenericReply to AuthRPCReply
* Remove authConfig.loginMethod and add authConfig.ServiceName
* Rename loginServer to AuthRPCServer
* Rename RPCLoginArgs to LoginRPCArgs
* Rename RPCLoginReply to LoginRPCReply
* Version and RequestTime are added to LoginRPCArgs and verified by
server side, not client side.
* Fix data race in lockMaintainence loop.
