Chrome Version:63.0.3236.0

Steps to reproduce the problem:
test_that DUT_IP platform_LogoutPerf

Expected result:
Expected output logs time taken to signout

Actual Result:
Test fails with runtime error.

How frequently does this problem reproduce? Always

Logs:
15:08:35 INFO | autoserv| INFO	----	----	kernel=4.4.86	localtime=Oct 13 15:08:35	timestamp=1507925315
15:08:35 INFO | autoserv| Installing autotest on ...
15:08:36 INFO | autoserv| Using installation dir /usr/local/autotest
15:08:37 INFO | autoserv| Installation of autotest completed from /build/reef/usr/local/build/autotest/client/
15:08:37 INFO | autoserv| Installing updated global_config.ini.
15:08:38 INFO | autoserv| Executing /usr/local/autotest/bin/autotest /usr/local/autotest/control phase 0
15:08:39 INFO | autoserv| Entered autotestd_monitor.
15:08:39 INFO | autoserv| Finished launching tail subprocesses.
15:08:39 INFO | autoserv| Finished waiting on autotestd to start.
15:08:39 INFO | autoserv| START	----	----	timestamp=1507925319	localtime=Oct 13 15:08:39
15:08:39 INFO | autoserv| START	platform_LogoutPerf	platform_LogoutPerf	timestamp=1507925319	localtime=Oct 13 15:08:39
15:08:40 INFO | autoserv| Bundling /build/reef/usr/local/build/autotest/client/site_tests/platform_LogoutPerf into test-platform_LogoutPerf.tar.bz2
15:08:52 INFO | autoserv| ERROR	platform_LogoutPerf	platform_LogoutPerf	timestamp=1507925332	localtime=Oct 13 15:08:52	Unhandled RuntimeError: Set changed size during iteration
15:08:52 INFO | autoserv| END ERROR	platform_LogoutPerf	platform_LogoutPerf	timestamp=1507925332	localtime=Oct 13 15:08:52
15:08:55 INFO | autoserv| END GOOD	----	----	timestamp=1507925335	localtime=Oct 13 15:08:55
15:08:55 INFO | autoserv| Got lock of exit_code_file.
15:08:55 INFO | autoserv| Released lock of exit_code_file and closed it.
15:08:57 INFO | autoserv| Client complete
15:08:58 INFO | autoserv| Finished processing control file