devstack/exercise.sh loops forever when there are more than 2 nodes

[Yuiko Takada]

When There are 2 nova nodes like these,

$ nova list
+--------------------------------------+---------+--------+------------+-------------+-----------------------------------------------------+
| ID | Name | Status | Task State | Power State | Networks |
+--------------------------------------+---------+--------+------------+-------------+-----------------------------------------------------+
| 17a59e88-e9d8-4f58-8817-be71388704c4 | testing | ERROR | - | NOSTATE | |
| f3a8e879-2eae-4970-88dd-8bb3d8a527f5 | testing | ACTIVE | - | Running | private=10.0.0.5, fda6:ea3e:21d6:0:5054:ff:fe16:5ca |
+--------------------------------------+---------+--------+------------+-------------+-----------------------------------------------------+

devstack/exercise.sh loops forever like:

+ for attempt in '{1..30}'
++ nova list
++ grep testing
++ awk '{ print $6; }'
+ status='ERROR
ACTIVE'
+ '[' 'ERROR
ACTIVE' = ERROR ']'
+ '[' 'ERROR
ACTIVE' '!=' ACTIVE ']'
+ '[' 10 -eq 30 ']'
+ sleep 30
+ for attempt in '{1..30}'
++ nova list
++ grep testing
++ awk '{ print $6; }'
+ status='ERROR
ACTIVE'
+ '[' 'ERROR
ACTIVE' = ERROR ']'
+ '[' 'ERROR
ACTIVE' '!=' ACTIVE ']'
+ '[' 11 -eq 30 ']'
+ sleep 30
...