qa/vstart_runner: fix mutiple 'timeout' option conflicting

qa/vstart_runner: fix mutiple 'timeout' option conflicting

The 'timeout' option in the environment may will conflict with the
ones in some ceph commands, like:

$ timeout 120 ./bin/ceph daemon mds.b session config 8718 timeout 45

And the old code will also give us incorrect result like:

['adjust-ulimits', 'ceph-coverage', 'timeout', '120', 'ceph', 'fs', 'dump']
will be transfered to:
['adjust-ulimits', 'ceph-coverage', '120', 'ceph', 'fs', 'dump']

The '120' is left behind.

Fixes: https://tracker.ceph.com/issues/44437
Signed-off-by: Xiubo Li <xiubli@redhat.com>
(cherry picked from commit 1bcd319496f507f76864a972c1de63439dd78d4a)