Fail bootstrap immediately if no topology found

Zero topologies might be found
if testbeds of some type are all unavailable,
or when purposedly restricted Change
is verified with a wrong trigger incantation.

The previous behavior enters an infinite cycle instead.

Change-Id: I9764a79ed4df57c6c99746438431bf1162b7f7ea
Signed-off-by: Vratko Polak <vrpolak@cisco.com>