This change is a simplification over existing
code since it is not required to have a separate
RPCClient structure instead keep authRPCClient can
do the same job.
There is no code which directly uses netRPCClient(),
keeping authRPCClient is better and simpler. This
simplication also allows for removal of multiple
levels of locking code per object.
Observed in #5160
* 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.
Disks when are offline for a long period of time, we should
ignore the disk after trying Login upto 5 times.
This is to reduce the network chattiness, this also reduces
the overall time spent on `net.Dial`.
Fixes#3286
