fix calculation of whether a project is cachable
fix calculation of whether a project is cachable

Summary:
Never cache first-party projects that use ShipIt.  Previously the code checked
the `shipit_fbcode_builder` property, which controlled whether or not
the `fbcode_builder` sources should be included in the project's ShipIt
mapping.  This setting is enabled for most but not all projects that use
ShipIt.

This resulted in projects that use ShipIt but that do not include the fbcode
builder sources being incorrectly cached.  This caused getdeps.py to not
run the SimpleShipitTransformerFetcher properly when their sources changed.

Reviewed By: wez

Differential Revision: D17493522

fbshipit-source-id: 57be5ac94ae44f56ccb3ce60ba23fac5d68bce0f

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift