Ktest: add email options to sample.config

A block of email options is added under the optional config section.

Link: http://lkml.kernel.org/r/1522094884-22718-5-git-send-email-tianyang.chen@oracle.com

Suggested-by: Dhaval Giani <dhaval.giani@oracle.com>
Signed-off-by: Tim Tianyang Chen <tianyang.chen@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>