Fixes: #9268
The new `SmbSession.list()` behavior prevents to pull files from sub-folders in inbound channel adapter
* Fix `SmbSession.list()` similar way to `SftpSession`: if `remoteFile.isFile()` then remove it as is.
Otherwise, perform `smbDir.listFiles()` on that sub-dir
* Modify `SmbTests.testSmbInboundFlow()` to poll files from the `smbSource/subSmbSource/`
(cherry picked from commit f2399a4e13)