core: fix start up policy loading race condition on perf standbys (#17801)

* core: fix start up policy loading race condition on perf standbys

* Use correct bool for perf standby

* changelog

changelog/17801.txt

@@ -0,0 +1,4 @@
+```release-note:bug
+core: fix a start up race condition where performance standbys could go into a 
+mount loop if default policies are not yet synced from the active node.
+```

vault/policy_store.go

@@ -264,6 +264,11 @@ func (c *Core) setupPolicyStore(ctx context.Context) error {
 		return nil
 	}
 
+	if c.perfStandby {
+		// Policies will sync from the active
+		return nil
+	}
+
 	// Ensure that the default policy exists, and if not, create it
 	if err := c.policyStore.loadACLPolicy(ctx, defaultPolicyName, defaultPolicy); err != nil {
 		return err