clevis-dracut: Add dependency on dracut, and use the trigger provided there

Thanks Thomas Lange for shedding some light on this issue.

debian/clevis-dracut.triggers

@@ -0,0 +1 @@
+activate-noawait update-initramfs

debian/control

@@ -62,6 +62,7 @@ Package: clevis-dracut
 Architecture: linux-any
 Depends: ${misc:Depends},
     clevis-systemd (= ${binary:Version}),
+    dracut,
     dracut-network,
 Description: Clevis integration for dracut
  Clevis is a plugable framework for automated decryption. This package