oo-trap-user: preserve quoting on shell commands

The new behavior of oo-trap-user stripped quoting and escaping from
incoming ssh commands, breaking certain functionality that depended on
commands running verbatim.

With the fix, the original command is preserved (with only whitespace
changes, same as previous behavior).

Bug 1156171 - oo-trap-user breaks ssh commands with quotes in them
https://bugzilla.redhat.com/show_bug.cgi?id=1156171
Merge pull request #5903 from jwhonce/stage

[TO_STAGE] oo-trap-user: preserve quoting on shell commands