tests/regression/tools/clear/test_ust fails occacionally

[Yu, Mingli]

Hi,

The lttng-tools test fails as below, is there anyone meet the same issue 
and how to fix this?  Thanks!


FAIL: tools/clear/test_ust 486 - Babeltrace succeeds
[snip]
FAIL: tools/clear/test_ust 706 - Babeltrace succeeds
[snip]
FAIL: tools/clear/test_ust
[snip]
# Wait for viewer to exit
not ok 486 - Babeltrace succeeds
FAIL: tools/clear/test_ust 486 - Babeltrace succeeds
#   Failed test 'Babeltrace succeeds'
#   in ./tools/clear/test_ust:test_ust_streaming_live_viewer() at line 324.
[snip]
# Wait for viewer to exit
not ok 706 - Babeltrace succeeds
FAIL: tools/clear/test_ust 706 - Babeltrace succeeds
#   Failed test 'Babeltrace succeeds'
#   in ./tools/clear/test_ust:test_ust_streaming_live_viewer() at line 324.


Thanks,
Mingli