tools: Adds option MAIL_SMTP_ENCRYPTION to notifier

Adds option MAIL_SMTP_ENCRYPTION to allow multiple types of SMTP
encryption to be specified in notifier config. This new option also
replaces old MAIL_ENABLE_SSL option.

Change-Id: I4a914091060c0a86b2710ce20e666d67f28fa401
Bug-Url: https://bugzilla.redhat.com/1020920
Signed-off-by: Martin Perina <mperina@redhat.com>