Add ENV var for ABS Polling Duration

[seamymckenna]

We are seeing it quite regularly that it is taking over the 10min mark to provision all the vms for the compliance demo environment so have introduced an env var that can be used to account for this. Tested as shown below and working as expected;

POLL_ABS_TIMEOUT_SECONDS=30

Starting: plan comply_demo::demo_01_provision_machines
Starting: task provision::abs on localhost
Finished: task provision::abs with 1 failure in 37.03 sec
Finished: plan comply_demo::demo_01_provision_machines in 37.04 sec
Failed on localhost:
  Timeout: unable to get a 200 response in 30 seconds
Failed on 1 target: localhost

unset POLL_ABS_TIMEOUT_SECONDS

Starting: plan comply_demo::demo_01_provision_machines
Starting: task provision::abs on localhost
Finished: task provision::abs with 0 failures in 562.12 sec

POLL_DURATION_TIMOUT_SECONDS=900

Starting: plan comply_demo::demo_01_provision_machines
Starting: task provision::abs on localhost
Finished: task provision::abs with 0 failures in 664.98 sec

[chelnak]

@seamymckenna Just want to check that the original path still works for users that don't want to set that timeout?