Increase events test timeout to more time as it fails often with timeout

The events test takes just under the 10 seconds. If there is some hiccup
on network or on the machine it self it common fails. Making it three
times longer should make running test more reliable.
4 jobs for steal-installed in 7 minutes and 5 seconds (queued for 1 second)
Name Stage Failure
test_busybox Test There is an unknown failure, please try again
/builds/turris/updater/tests/check/src/check_msg.c:247: warning: the use of `tempnam' is dangerous, better use `mkstemp'
mkdir -p ./testdir
SUPPRESS_LOG=1 S=. TMPDIR=/builds/turris/updater/testdir COVERAGEDIR=/builds/turris/updater/.lua_coverage bin/ctest-events
Running suite(s): Event loop
99%: Checks: 1057, Failures: 1, Errors: 0
tests/events.c:161:F:commands:command_start_noio:0: Assertion 'CK_TERMINATED == infos[i].killed' failed: CK_TERMINATED == 0, infos[i].killed == 1
make: *** [test-c-events] Error 1
tests/Makefile.dir:129: recipe for target 'test-c-events' failed
ERROR: Job failed: exit code 1