Make dep resource sync optional if it's already synced previously

[soichih]

Currently, a task would fail to start up if any of the input resources are in non-OK status when it tries to sync inputs datasets even thouogh they are previously synced.

source resource status is non-ok .. will retry later

This is sad, because the task could be executed on active resource with previously synced input datasets and it's very rare that input datasets are modified.

To see if the input datasets are already synced, we can just look at dep.resource_ids, and if target resource id is listed there (the input dataset is already staged), make dataset syncing optional.