main: open cmdmon and NTP internet sockets before dropping root

Call the CAM, NIO, NCR initialization functions and setup the access
restrictions before root is dropped. This will be needed on NetBSD,
where it's not possible to bind sockets to privileged ports without the
root privileges. Split the creation of the Unix domain command socket
from the CAM initialization to keep the chrony user as the owner of the
socket.

cmdmon.h

@@ -33,6 +33,7 @@ extern void CAM_Initialise(int family);
 
 extern void CAM_Finalise(void);
 
+extern void CAM_OpenUnixSocket(void);
 extern int CAM_AddAccessRestriction(IPAddr *ip_addr, int subnet_bits, int allow, int all);
 extern int CAM_CheckAccessRestriction(IPAddr *ip_addr);