Use computer name and serial id to construct default mac client name
Use computer name and serial id to construct default mac client name

(cherry picked from commit 11e5e7fe4bc8a3dc0547aec4e5ef4d2704502c51)

uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend