When calling an import which is an exported wasm function, the
interpreter needs to look through the jump table to find the
actual code object.
We already had that logic for indirect calls, but it was missing for
imported calls.

R=ahaas@chromium.org

Bug: chromium:860392
Change-Id: I6b5a0192f79c23cb1de55407fe93f6df9a17235a
Reviewed-on: https://chromium-review.googlesource.com/1127671Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54291}