Cleanup: removed separate no-scrape marker file

Changed prefix file format to allow encoding of no-scrape request
using "# disabled" pseudo comment. Single automatic routing medata
file makes proper synchronization easier to implement and simplifies
overall implementation.

This also eliminated two HEAD requests per remote (due to a bug
original implementation performed HEAD no-scrape file for each
discovery strategy, not once per remote).

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>
Cleanup: reconciled autorouting startup and periodic update logic

Automatic routing periodic update logic is now able to initialize
hosted repository prefix path list as needed. No need to do this
explicitly during startup any more.

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>