Added submodule for go-smtpd
[#59695164]

Signed-off-by: Damien Le Berrigaud <damien@pivotallabs.com>
Replace http interface for alerts with smtp server
[#59695164]

Signed-off-by: Damien Le Berrigaud <damien@pivotallabs.com>
Added monit config for smtp alerts with go agent

Signed-off-by: Damien Le Berrigaud <damien@pivotallabs.com>