BasePackConnection::readAdvertisedRefsImpl was creating an exception by
calling `noRepository`, and then blindly calling `initCause` on it. As
`noRepository` can be overridden, it's not guaranteed to be missing a
cause.
BasePackPushConnection overrides `noRepository` and initiates a fetch,
which may throw a `NoRemoteRepositoryException` with a cause.
In this case calling `initCause` threw an `IllegalStateException`.
In order to throw the correct exception, we now return the
BasePackPushConnection exception and suppress the one thrown by
BasePackConnection
Bug: 578511
Change-Id: Ic1018b214be1e83d895979ee6c7cbce3f6765f6f
78c9b9260a