The random space in rand_name is too small

Looks like when you using hundreds of name just in 1000000 element space the name collusion can happen and generates false negative results.

It is also can be related with improper teardown.

Several solution is possible:
* Record all generated names, and run the function again if one reoccurs.
   - Drawback needs: more memory.
   - Can collide with names from improper teardown from previous tempest execution

* Increase the random space.
 - Does not grantee uniqueness, but mitigate the collision chance
 - UUID make the names much longer

* Incremental name:
 - Not really use random, just increment a global number in every request
 - Can collide with residues from previous execution

* Combination incremental and random solution together
 - the unique like part are constructed from a random number generated once in every execution + an incrementing global number

Additional improvement:
The rand_name should use dashes between the name and unique like part without an explicit request.