tools: notifier - add validation to mail type properties

Creating smtp requests with FROM/USER properties set to values not in the format
user@domain will fail, so we now enforce it the the bash script
*?@?* means that there must be a @ with at least one char on each side

Change-Id: I652d6b7aa9ca34192d6892174bf57b11335cb98a
Bug-Url: https://bugzilla.redhat.com/885436
Signed-off-by: Noam Slomianko <nslomian@redhat.com>