Replace all instances of rpcclient.ClientConnector with birpc.ClientConnector.
Pass context, maxReconnectInterval, delayFunc and birpcClient to rpcclient
constructors.
Remove redundant time.Duration conversions (e.g. time.Duration(1*time.Second)
now becomes time.Second.
Add context where needed (context.Background() for tests, context.TODO()
for places where it should be passed from somewhere else).
Implement that functionality of the SessionSv1.Sleep call, in sessions/sessions
instead of apier/v1.
Make changes in utils/server.go (replacing the old rpc2 library with github.com/cgrates/birpc).
Change the way we register birpc methods for sessions in services, using a helper function
defined in engine/libengine.go.
A time.Sleep() of 10 milliseconds has been added after starting the services in order to wait for the goroutine that handles reloads to get instantiated. This solves the occasional deadlock that happens when a reload signal is sent to a subsystem that requires storDB before sending it to storDB itself. One consequence of waiting is that where we previously expected the DataDB service to not be running yet, now it has enough time.
