keep trailing delimiter with SFTP open

[JacobBarthelmeh]

ZD 18566

Fix for SFTP cases with trailing delimiter.

OpenSSH client 9.6 (which does a SFTP command instead of SCP, -O restores using SCP protocol)

mkdir /tmp/subfolder
scp /tmp/test.txt [email protected]:/tmp/subfolder/test/

Before this change wolfSSH would allow test.txt to be copied to /tmp/subfolder/test. After this change the command correctly fails.