Fixed some tests

Code change:
- Do not start the processMirrorMsgs and processSourceMsgs go routine
if the server has been detected to be shutdown. This would otherwise
leave some go routine running at the end of some tests.
- Pass the fch and qch to the consumerFileStore's flushLoop otherwise
in some tests this routine could be left running.

Tests changes:
- Added missing defer NATS connection close
- Added missing defer server shutdown

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

server/jetstream_leafnode_test.go

@@ -1206,7 +1206,7 @@ default_js_domain: {B:"DHUB"}
 	require_Equal(t, si.Cluster.Name, "HUB")
 }
 
-func TestLeafNodeSvcImportExportCycle(t *testing.T) {
+func TestJetStreamLeafNodeSvcImportExportCycle(t *testing.T) {
 	accounts := `
 	accounts {
 		SYS: {