fix(deb): support installation with no systemd

Author: lucarin91

debian/router/DEBIAN/postinst

@@ -1,5 +1,8 @@
 #!/bin/sh
 
-systemctl daemon-reload
 systemctl enable arduino-router
-systemctl start arduino-router
+
+if [ -d /run/systemd/system ]; then
+  systemctl daemon-reload
+  systemctl start arduino-router
+fi

debian/router/DEBIAN/postrm

@@ -1,3 +1,5 @@
 #!/bin/sh
 
-systemctl daemon-reload
+if [ -d /run/systemd/system ]; then
+  systemctl daemon-reload
+fi

debian/router/DEBIAN/prerm

@@ -1,4 +1,7 @@
 #!/bin/sh
 
 systemctl disable arduino-router
-systemctl stop arduino-router
+
+if [ -d /run/systemd/system ]; then
+  systemctl stop arduino-router
+fi