Change processlist query to support ONLY_FULL_GROUP_BY sql_mode (#684)

Otherwise "Error 1055: 'information_schema.processlist.HOST' isn't in GROUP BY" is raised.

Signed-off-by: René Scheibe <rene.scheibe@gmail.com>

collector/info_schema_processlist.go

@@ -38,7 +38,7 @@ const infoSchemaProcesslistQuery = `
 		  FROM information_schema.processlist
 		  WHERE ID != connection_id()
 		    AND TIME >= %d
-		  GROUP BY user, SUBSTRING_INDEX(host, ':', 1), command, state
+		  GROUP BY user, host, command, state
 	`
 
 // Tunable flags.