Fix machine volumes with long path and paths with dashes

AppleHV accepts a max 36 bytes for mount tags. Instead of using the fully qualified path for the mount tag, SHA256 the path, and truncate the shasum to 36 bytes.
Also correctly escape dashes in mounted paths.

Signed-off-by: Ashley Cui <acui@redhat.com>

pkg/systemd/parser/unitfile.go

@@ -932,3 +932,9 @@ func (f *UnitFile) GetTemplateParts() (string, string) {
 	}
 	return parts[0] + "@" + ext, parts[1]
 }
+
+func PathEscape(path string) string {
+	var escaped strings.Builder
+	escapeString(&escaped, path, true)
+	return escaped.String()
+}