Comment 0 for bug 1517939

dos.py creates a new env despite of exception that's related to improper network pool.
Probably the same behavior can be observed in other similar cases.
This pollutes the env namespace and prevents from creating the new env with the same name with valid data after correction.

Steps to reproduce:
0. check if no 'foo' env via: dos.py list
1. dos.py create --iso-path <path to iso> --node-count 3 --vcpu 4 --ram 4096 --admin-vcpu 4 --admin-ram 4096 --net-pool <improper net pool> foo
2. check if 'foo' env is in 'dos.py list' output

Expected Behavior: env shouldn't be created and added to the namespace in case of exceptions during creation

Actual Behavior: env is created and added to the namespace

(fuel-devops-venv)me@it:~$ dos.py create --iso-path /path/to/iso --node-count 3 --vcpu 4 --ram 4096 --admin-vcpu 4 --admin-ram 4096 --net-pool 10.109.0.0/29:10.109.0.0/27 moo
Traceback (most recent call last):
  File "/home/me/fuel-devops-venv/bin/dos.py", line 22, in <module>
    main()
  File "/home/me/fuel-devops-venv/local/lib/python2.7/site-packages/devops/shell.py", line 527, in main
    Shell(args).execute()
  File "/home/me/fuel-devops-venv/local/lib/python2.7/site-packages/devops/shell.py", line 41, in execute
    self.commands.get(self.params.command)(self)
  File "/home/me/fuel-devops-venv/local/lib/python2.7/site-packages/devops/shell.py", line 174, in do_create
    prefix=int(prefix))
ValueError: invalid literal for int() with base 10: '10.109.0.0/27'
(fuel-devops-venv)me@it:~$ dos.py list
NAME
------------------------
fuelweb_test_system_test
moo

(fuel-devops-venv)me@it:~$ dos.py version
2.9.12