acessman: improve access manager logging and error handling

This commit adds logs to the new access manager. This'll help us monitor
the new system behavior, and may make debugging easier in the future.

log.go

@@ -99,6 +99,7 @@ var (
 	rpcsLog = addLndPkgLogger("RPCS")
 	srvrLog = addLndPkgLogger("SRVR")
 	atplLog = addLndPkgLogger("ATPL")
+	acsmLog = addLndPkgLogger("ACSM")
 )
 
 // genSubLogger creates a logger for a subsystem. We provide an instance of