INT-3066 Fix NPE During Connection Recovery

The JmsOutboundGateway's Listener container could throw
an NPE during connection recovery - while logging recovery
status.

The log attempts to include the destination description which
throws the NPE if there is no destination yet established.

Only attempt to get the description if the destination has
been established. And, even then, use a try/catch block
to prevent the NPE. Log the destination as 'null' in this
case.

Add a test case to detect the NPE by adding an ErrorHandlingTaskExecutor.

No errors should be detected with the fix in place.
INT-3089 Fix FileExistsMode.IGNORE

When writing files with this mode setting, the FWMH detected
that the final file already exists, but did not detect that
the temporary (default ....writing) file exists. This could
happen if two adapters were simulataneously processing the same
file.

Also, while a comment in the setter said an empty temp file
suffix is allowed, it did not work because the file rename
is performed unconditionally, fails, and throws an exception.

Add a check for the temporary file (if the suffix is not "").

Don't rename if the file was written in-place (no temp file suffix).

Add test cases for the FileExistsMode.IGNORE for both the final
and temporary files. Add a test where the temporary file suffix
is "", a ...writing file exists, the final file does not exist
and so is created by the handler. The ...writing file is untouched.
INT-3061 Update Reference Copyright