Verified with latest #74-mitaka, the issue not seen  and please find below the sanity logs captured for 
failed #50 and current scenario #74,   Marking the bug state accordingly lowering priority

failed mitaka #50 (sanity-logs), 
2017-08-31 14:11:15,467 - DEBUG - Check whether image by uuid 193f9d0d-60a0-4c9b-8b72-7c5bdd652295 is active
2017-08-31 14:11:18,971 - INFO - VM ([<Server: vm1>]) created on node: (5a10s23), Zone: (nova:5a10s23)
2017-08-31 14:11:19,875 - DEBUG - Check whether image by uuid 193f9d0d-60a0-4c9b-8b72-7c5bdd652295 is active
2017-08-31 14:11:22,855 - INFO - VM ([<Server: vm2>]) created on node: (5a10s23), Zone: (nova:5a10s23)
2017-08-31 14:11:23,890 - DEBUG - Check whether image by uuid 193f9d0d-60a0-4c9b-8b72-7c5bdd652295 is active
2017-08-31 14:11:26,021 - INFO - VM ([<Server: vm3>]) created on node: (5a10s23), Zone: (nova:5a10s23)
2017-08-31 14:11:27,166 - DEBUG - Check whether image by uuid 193f9d0d-60a0-4c9b-8b72-7c5bdd652295 is active
2017-08-31 14:11:29,410 - INFO - VM ([<Server: vm4>]) created on node: (5a10s23), Zone: (nova:5a10s23)




current #74-mitaka same tests with VM launch distributed across computes in round-robbin,
2017-09-11 14:32:16,728 - INFO - VM ([<Server: vm1>]) created on node: (5a10s23), Zone: (nova:5a10s23)
2017-09-11 14:32:24,230 - INFO - VM ([<Server: vm2>]) created on node: (5a10s01b), Zone: (nova:5a10s01b)
2017-09-11 14:32:26,985 - INFO - VM ([<Server: vm3>]) created on node: (5a10s29), Zone: (nova:5a10s29)
2017-09-11 14:32:29,002 - INFO - VM ([<Server: vm4>]) created on node: (5a10s23), Zone: (nova:5a10s23)


root@5a10s31:/etc/apt# nova availability-zone-list
+-----------------------+----------------------------------------+
| Name                  | Status                                 |
+-----------------------+----------------------------------------+
| internal              | available                              |
| |- 5a10s29            |                                        |
| | |- nova-conductor   | enabled :-) 2017-09-11T21:38:18.000000 |
| | |- nova-consoleauth | enabled :-) 2017-09-11T21:38:09.000000 |
| | |- nova-scheduler   | enabled :-) 2017-09-11T21:38:09.000000 |
| | |- nova-console     | enabled :-) 2017-09-11T21:38:09.000000 |
| |- 5a10s30            |                                        |
| | |- nova-conductor   | enabled :-) 2017-09-11T21:38:13.000000 |
| | |- nova-consoleauth | enabled :-) 2017-09-11T21:38:14.000000 |
| | |- nova-scheduler   | enabled :-) 2017-09-11T21:38:14.000000 |
| | |- nova-console     | enabled :-) 2017-09-11T21:38:14.000000 |
| |- 5a10s31            |                                        |
| | |- nova-conductor   | enabled :-) 2017-09-11T21:38:09.000000 |
| | |- nova-consoleauth | enabled :-) 2017-09-11T21:38:11.000000 |
| | |- nova-scheduler   | enabled :-) 2017-09-11T21:38:10.000000 |
| | |- nova-console     | enabled :-) 2017-09-11T21:38:11.000000 |
| nova                  | available                              |
| |- 5a10s01b           |                                        |
| | |- nova-compute     | enabled :-) 2017-09-11T21:38:14.000000 |
| |- 5a10s23            |                                        |
| | |- nova-compute     | enabled :-) 2017-09-11T21:38:10.000000 |
| |- 5a10s29            |                                        |
| | |- nova-compute     | enabled :-) 2017-09-11T21:38:17.000000 |
+-----------------------+----------------------------------------+
root@5a10s31:/etc/apt#