Fix various poolmeta races (#18230)

There is a fundamental race condition in `newErasureServerPools`, where setObjectLayer is 
called before the poolMeta has been loaded/populated.

We add a placeholder value to this field but disable all saving of the value, so we don't risk 
overwriting the value on disk. Once the value has been loaded or created, it is replaced with 
the proper value, which will also be saved.

Also fixes various accesses of `poolMeta` that were done without locks.

We make the `poolMeta.IsSuspended` return false, even if we shouldn't risk out-of-bounds 
reads anymore.

cmd/erasure-server-pool.go

@@ -143,6 +143,12 @@ func newErasureServerPools(ctx context.Context, endpointServerPools EndpointServ
 
 	z.decommissionCancelers = make([]context.CancelFunc, len(z.serverPools))
 
+	// Initialize the pool meta, but set it to not save.
+	// When z.Init below has loaded the poolmeta will be initialized,
+	// and allowed to save.
+	z.poolMeta = newPoolMeta(z, poolMeta{})
+	z.poolMeta.dontSave = true
+
 	// initialize the object layer.
 	setObjectLayer(z)