check_dhcp: fix mac address and interface number detection on solaris

newer (or x86) solaris implementations have interface names like e1000g0
which includes numbers. So we reverse the interface number detection to
get the last number, instead of the first number.

plugins-root/check_dhcp.c

@@ -372,11 +372,16 @@ int get_hardware_address(int sock,char *interface_name){
 	char *p;
 	int unit;
 
-	for(p = interface_name; *p && isalpha(*p); p++)
-		/* no-op */ ;
-	if( p != '\0' ){
+    /* get last number from interfacename, eg lnc0, e1000g0*/
+    int i;
+    p = interface_name + strlen(interface_name) -1;
+	for(i = strlen(interface_name) -1; i > 0; p--) {
+		if(isalpha(*p))
+            break;
+    }
+    p++;
+	if( p != interface_name ){
 		unit = atoi(p) ;
-		*p = '\0' ;
 		strncat(dev, interface_name, 6) ;
 		}
 	else{