Clean-up StrategicPriority & MembershipCoordination on import

[thenav56]

Addresses Legacy dataset Related to:

• https://github.com/IFRCGo/go-api/pull/2170

Changes

• Clean-up existing dataset (StrategicPriority & MembershipCoordination)
• Add transaction.atomic over whole import process

[thenav56]

Hey @szabozoltan69, Could you review this PR? This should fix the inconsistency in Strategic dashboard mentioned by @tovari.

[szabozoltan69]

Merged and deployed to Staging, also https://goadmin-stage.ifrc.org/en/admin/country_plan/dataimport/ used afterwise.