Fix utf8 4 byte collation method

The default collate method used by the mysql puppet module is not
compatbile with our 4 byte encoding. Update the collate method to match
the 4 byte encoding.

Change-Id: I8f65316ba609ecf30c9797d631bdeb4a083b16ce

manifests/mysql.pp

@@ -23,6 +23,7 @@ class etherpad_lite::mysql(
     host     => 'localhost',
     grant    => ['all'],
     charset  => 'utf8mb4',
+    collate  => 'utf8mb4_unicode_ci',
     require  => [
       Class['mysql::server'],
       Class['mysql::server::account_security'],