As a user my sync continues in case it encounters corrupted manifest

[ipanova]

Is your feature request related to a problem? Please describe.
Right now the sync of the whole repo fails when it encounters at least one corrupted manifest

Describe the solution you'd like
I would like the sync to continue and in the task details record what manifests were skipped.
In case a manifest list is corrupted, whole manifest will be skipped including its all per-arch manifests.

Additional context
This logic should probably be incompatible with mirror=True

[lubosmj]

This will be much harder to accomplish once we add validation for synced manifests (e.g., initiating a skip task for a parent manifest list that was already parsed and validated). We need to reevaluate the complexity of this issue.