lava: handle reaching max number of retry for submit operation

lava: handle reaching max number of retry for submit operation

Reaching the maximum number of retry would lead to:

 Traceback (most recent call last):
   File "/home/jenkins/workspace/vm_tests_kcanary_lcanary/src/lttng-ci/scripts/system-tests/lava2-submit.py", line 322, in <module>
     sys.exit(main())
   File "/home/jenkins/workspace/vm_tests_kcanary_lcanary/src/lttng-ci/scripts/system-tests/lava2-submit.py", line 284, in main
     print('Lava jobid:{}'.format(jobid))
 UnboundLocalError: local variable 'jobid' referenced before assignment

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>