Problems with ProxyCommand

[DrYak <doktor.yak@xxxxxxxxx>]

see https://bugs.kde.org/show_bug.cgi?id=273397

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When using a "ProxyCommand" option, libssh requires the command to be
quoted (i.e: ' ProxyCommand "ssh -q -A -X -W %h:%p JUMPHOST" ') for the
whole line to be used (otherwise only "ssh" is called).

i.e.: on the quoted string is loaded, everything else following the
blank is discarded. Parameters are split between blanks inside the
quoted string.

Result:
- kio_sftp (which is libssh-based) works
- ssh complains it can't find an executable named "ssh -q -A -X -W %h:%p
JUMPHOST" and fails.

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This differs from ssh's own behaviour, where command should NOT be
quoted (i.e: ' ProxyCommand ssh -q -A -X -W %h:%p JUMPHOST '), otherwise
the whole quoted string is interpreted as the executable name.

i.e: the whole line is loaded and parameters are split between blanks
outside the string.

Resuot:
- ssh works as it should
- kio_sftp only runs "ssh" without any option and gets the "ssh usage"
as an error and fails.