deploy: allow specifying a different user to run the tester
deploy: allow specifying a different user to run the tester

Not sure if this is particularly useful, and it has the disadvantage
of triggering an interactive session even if you're okay with the
default user "patchew".  But I'm throwing it out just in case
(for example if you want tests running as root (!)).

Signed-off-by: Paolo Bonzini <69d3ebcf5ee4e7f05a50dc23cd96655b730804b4@redhat.com>
Message-Id: <20180313174545.14341-6-69d3ebcf5ee4e7f05a50dc23cd96655b730804b4@redhat.com>
Signed-off-by: Fam Zheng <df9fd617995bad07eac70e27aa3fe5069270e3bd@redhat.com>

pvital/patchew,pvital/patchew,pvital/patchew,pvital/patchew