Remove calls to getCallsign() from repository daemons

Summary: Ref T4245. These are all descriptive or UI-facing.

Test Plan:

• Ran bin/repository pull ... with various identifiers.
• Ran bin/repository mirror ... with various identifiers.
• Ran bin/repository discover ... with various identifiers.
• Ran bin/phd debug pull X Y --not Z with various identifiers.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4245

Differential Revision: https://secure.phabricator.com/D14926