Clarify docs re output of ssh hostname commands
Clarify docs re output of ssh hostname commands

Fixes #3348. Supersedes #3417.

Replace the word app with the word server in last line of doc to further
clarify that line.

ehartsuyker/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,conorsch/securedrop,conorsch/securedrop,heartsucker/securedrop,heartsucker/securedrop,conorsch/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,conorsch/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,conorsch/securedrop