Add mention of MINA as alternate sshd.backend option beside NIO2 in doc
Add mention of MINA as alternate sshd.backend option beside NIO2 in doc

The default value for that option was changed to NIO2 in I48c69dd3, but
MINA was not mentioned back as the alternative.

Change-Id: I2ef3a6278d56cea10f0a277980500c6688617f6d

MerritCR/merrit,MerritCR/merrit,gerrit-review/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,MerritCR/merrit,joshuawilson/merrit,MerritCR/merrit,MerritCR/merrit,joshuawilson/merrit,joshuawilson/merrit,MerritCR/merrit,joshuawilson/merrit,WANdisco/gerrit,gerrit-review/gerrit,joshuawilson/merrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,joshuawilson/merrit,gerrit-review/gerrit,joshuawilson/merrit,GerritCodeReview/gerrit,WANdisco/gerrit,MerritCR/merrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,gerrit-review/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,WANdisco/gerrit,joshuawilson/merrit,WANdisco/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,gerrit-review/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,MerritCR/merrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit