refstack_result is used to register result of running
refstack-client, however, it was used in 2 different tasks one of
which was always skipped. There may happen a situation (when the
latter task is skipped), the skipped task overrides the result
of the refstack-client execution from the other task.
The patch fixes that by using a different variable for each of
the tasks running refstack-client.
Change-Id: I6f524df674dfbb2d6b9372dce51f1e1aec8ed9be
f865af4563