Longhorn: Upgrade from 1.6.4. to 1.7.3

Change-Id: I4e713a453a6b9e983685e2db550066fd2694609f
diff --git a/charts/longhorn/templates/ingress.yaml b/charts/longhorn/templates/ingress.yaml
index 9038ff0..61175e8 100644
--- a/charts/longhorn/templates/ingress.yaml
+++ b/charts/longhorn/templates/ingress.yaml
@@ -22,7 +22,7 @@
     http:
       paths:
         - path: {{ default "" .Values.ingress.path }}
-          pathType: ImplementationSpecific
+          pathType: {{ default "ImplementationSpecific" .Values.ingress.pathType }}
           backend:
             service:
               name: longhorn-frontend