Add support for Initialisation Scripts with rcS (#340)

* validate systemctl command

* validate systemctl command

* add rcS support

* only attempt to set environment if list is not empty

* check if service bin exists

service_linux.go

@@ -62,6 +62,15 @@ func init() {
 			},
 			new: newOpenRCService,
 		},
+		linuxSystemService{
+			name:   "linux-rcs",
+			detect: isRCS,
+			interactive: func() bool {
+				is, _ := isInteractive()
+				return is
+			},
+			new: newRCSService,
+		},
 		linuxSystemService{
 			name:   "unix-systemv",
 			detect: func() bool { return true },