vm tests: avoid leaving /tmp/blechs.recovery behind

There's code that expects P_VDSM_VAR_RUN to end with a slash.

Change-Id: I73e7628be87692d17a6a5f629c3370df37e22dc8
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/26197
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-by: Francesco Romani <fromani@redhat.com>