ImapMailReceiver: Check folder.isOpen before idle

Increase wait timeout for message in the ImapMailReceiverTests

https://build.spring.io/browse/INT-MASTERSPRING40-556/

Author: artembilan

spring-integration-mail/src/main/java/org/springframework/integration/mail/ImapMailReceiver.java

@@ -179,7 +179,9 @@ else if (!folder.getPermanentFlags().contains(Flags.Flag.RECENT)) {
 		try {
 			this.pingTask = this.scheduler.schedule(this.idleCanceler,
 					new Date(System.currentTimeMillis() + this.cancelIdleInterval));
-			imapFolder.idle();
+			if (imapFolder.isOpen()) {
+				imapFolder.idle();
+			}
 		}
 		finally {
 			imapFolder.removeMessageCountListener(this.messageCountListener);

spring-integration-mail/src/test/java/org/springframework/integration/mail/ImapMailReceiverTests.java

@@ -250,7 +250,7 @@ public void testIdleWithServerGuts(ImapMailReceiver receiver, boolean mapped, bo
 				assertThat(received.getPayload(), equalTo(TestMailServer.MailServer.MailHandler.MESSAGE + "\r\n"));
 			}
 		}
-		assertNotNull(channel.receive(10000)); // new message after idle
+		assertNotNull(channel.receive(20000)); // new message after idle
 		assertNull(channel.receive(100)); // no new message after second and third idle
 		verify(logger).debug("Canceling IDLE");