INT-3091 Fix Concurrent (S)FTP Transfers

byte[] and String payloads were written to a temporary file.

If the same message is transferred to two different destinations
concurrently, one of the adapters could remove the temporary
file while the other was using it.

Don't use a temporary file for these payloads, simply use the
payload byte[] [or a String.getBytes()] as the InputStream
passed to the Session.write() method.

Conflicts:

	spring-integration-file/src/main/java/org/springframework/integration/file/remote/handler/FileTransferringMessageHandler.java
	spring-integration-file/src/main/java/org/springframework/integration/file/remote/synchronizer/AbstractInboundFileSynchronizer.java
	spring-integration-ftp/src/test/java/org/springframework/integration/ftp/config/FtpOutboundChannelAdapterParserTests.java
	spring-integration-ftp/src/test/java/org/springframework/integration/ftp/config/FtpsOutboundChannelAdapterParserTests.java
	spring-integration-sftp/src/test/java/org/springframework/integration/sftp/config/OutboundChannelAdapterParserTests.java

Resolved.

Polishing