Guard against removing a hold while the package manager is busy.
Test:
1. Place hold on freedombox package.
2. Wait 3 minutes in development mode.
- Package is held.
3. Touch /var/lib/freedombox/package-held.
4. Wait 3 minutes in development mode.
- Package is not held.
- Flag is removed.
Signed-off-by: James Valleroy <jvalleroy@mailbox.org>