Use puppet 4 compatible mysql functions

These was introduced in 6.0.0 and is required to
support later version of puppetlabs-mysql.

Change-Id: I01e3c803ef1aae428be01d7984efe0012aabd0f9

manifests/db/mysql.pp

@@ -49,7 +49,7 @@ class panko::db::mysql(
 
   ::openstacklib::db::mysql { 'panko':
     user          => $user,
-    password_hash => mysql_password($password),
+    password_hash => mysql::password($password),
     dbname        => $dbname,
     host          => $host,
     charset       => $charset,

metadata.json

@@ -9,6 +9,10 @@
             "name": "puppetlabs/stdlib",
             "version_requirement": ">=5.0.0 <6.0.0"
         },
+        {
+            "name": "puppetlabs/mysql",
+            "version_requirement": ">=6.0.0 <9.0.0"
+        },
         {
             "name": "openstack/keystone",
             "version_requirement": ">=14.2.0 <15.0.0"

releasenotes/notes/puppet4-mysql-func-361ea787e56650ee.yaml

@@ -0,0 +1,4 @@
+---
+upgrade:
+  - |
+    This module now requires a puppetlabs-mysql version >= 6.0.0