[commands] max_concurrency comes before cooldowns

Fix #6172

discord/ext/commands/core.py

@@ -778,6 +778,9 @@ class Command(_BaseCommand):
         if not await self.can_run(ctx):
             raise CheckFailure('The check functions for command {0.qualified_name} failed.'.format(self))
 
+        if self._max_concurrency is not None:
+            await self._max_concurrency.acquire(ctx)
+
         if self.cooldown_after_parsing:
             await self._parse_arguments(ctx)
             self._prepare_cooldowns(ctx)
@@ -785,9 +788,6 @@ class Command(_BaseCommand):
             self._prepare_cooldowns(ctx)
             await self._parse_arguments(ctx)
 
-        if self._max_concurrency is not None:
-            await self._max_concurrency.acquire(ctx)
-
         await self.call_before_hooks(ctx)
 
     def is_on_cooldown(self, ctx):