fixed failing systemd commands

Makefile

@@ -18,7 +18,7 @@ clean:
 	rm -f $(TARGETS) $(OBJ)
 
 install:
-	systemctl stop dhcp_protect
+	systemctl stop dhcp_protect || true
 	cp dhcp_protect /usr/local/bin/
 	cp dhcp_protect.conf /usr/local/etc/
 	cp dhcp_protect.service /etc/systemd/system/
@@ -27,8 +27,8 @@ install:
 	systemctl start dhcp_protect
 
 uninstall:
-	systemctl stop dhcp_protect
-	systemctl disable dhcp_protect
+	systemctl stop dhcp_protect || true
+	systemctl disable dhcp_protect || true
 	rm -f /usr/local/bin/dhcp_protect
 	rm -f /usr/local/etc/dhcp_protect.conf
 	rm -f /etc/systemd/system/dhcp_protect.service