Make tests more reliable (#2948)

When using `testrig.CreateBase` and then using that base for other
`NewInternalAPI` calls, we never actually shutdown the components.
`testrig.CreateBase` returns a `close` function, which only removes the
database, so still running components have issues connecting to the
database, since we ripped it out underneath it - which can result in
"Disk I/O" or "pq deadlock detected" issues.

setup/base/base.go

@@ -264,6 +264,8 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string, options ...Base
 
 // Close implements io.Closer
 func (b *BaseDendrite) Close() error {
+	b.ProcessContext.ShutdownDendrite()
+	b.ProcessContext.WaitForShutdown()
 	return b.tracerCloser.Close()
 }