virtfs: only install by default, if virt environment detected

modules.d/95virtfs/module-setup.sh

@@ -10,7 +10,21 @@ check() {
         return 1
     }
 
-    return 0
+    if type -P systemd-detect-virt >/dev/null 2>&1; then
+        vm=$(systemd-detect-virt --vm >/dev/null 2>&1)
+        (($? != 0)) && return 255
+        [[ $vm = "qemu" ]] && return 0
+        [[ $vm = "kvm" ]] && return 0
+        [[ $vm = "bochs" ]] && return 0
+    fi
+
+    for i in /sys/class/dmi/id/*_vendor; do
+        [[ -f $i ]] || continue
+        read vendor < $i
+        [[  "$vendor" == "QEMU" ]] && return 0
+        [[  "$vendor" == "Bochs" ]] && return 0
+    done
+    return 255
 }
 
 depends() {