Increase delay for zed log in events tests

Increase delay for zed log in events tests

In zed event test cases, a brief delay was introduced
to allow for events to make it to the zed log. On at least
one buildbot builder, the 1 second delay is not long enough.
Therefore, increasing the delay should ensure the zed has
more than enough time to write to its log.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes #6395