cmdmon: refactor command authorization checks

Try to simplify the code and make it more robust to potential bugs.

Instead of maintaing a table mapping all commands to open/auth
permissions, use a short list of open commands. Split the processing
of the commands into two groups, read-write commands and read-only
(monitoring) commands, where the first group is processed only with full
access. Check both the socket descriptor and address type before giving
full access. While moving the code, reorder the commands alphabetically.

candm.h

@@ -510,13 +510,6 @@ typedef struct {
 
 } CMD_Request;
 
-/* ================================================== */
-/* Authority codes for command types */
-
-#define PERMIT_OPEN 0
-#define PERMIT_LOCAL 1
-#define PERMIT_AUTH 2
-
 /* ================================================== */
 
 /* Reply codes */