Configure etherpad to use utf8mb4

We need to set this in the settings.json.

While we're there, set the defaults in my.cnf. I don't think that
actually matters, but it also shouldn't hurt.

Change-Id: I52e65136383f6c06d1693dd3d396f527c7e0b377

playbooks/roles/etherpad/files/my.cnf

@@ -1,6 +1,6 @@
 [client]
 # Default is Latin1, if you need UTF-8 set this (also in server section)
-default-character-set = utf8
+default-character-set = utf8mb4
 
 [mysqld]
 wait_timeout = 28800
@@ -9,7 +9,7 @@ wait_timeout = 28800
 #
 # Default is Latin1, if you need UTF-8 set all this (also in client section)
 #
-character-set-server  = utf8
-collation-server      = utf8_bin
-character_set_server   = utf8
-collation_server       = utf8_bin
+character-set-server  = utf8mb4
+collation-server      = utf8mb4_bin
+character_set_server   = utf8mb4
+collation_server       = utf8mb4_bin

playbooks/roles/etherpad/templates/settings.json.j2

@@ -26,6 +26,7 @@
                    "user"    : "{{ etherpad_db_user }}",
                    "host"    : "localhost",
                    "password": "{{ etherpad_db_password }}",
+                   "charset" : "utf8mb4",
                    "database": "etherpad-lite"
                  },
   //the default text of a pad