Use the build directory to decide which result is the correct one.

If the indel_detection_strategy contains an unfiltered detector that
also detects snvs, the previous logic would get confused about which
result is the correct one.  The final result symlinked in the variants
directory knows the one true result.

(In SomVal a different label is set on the SR::User--this would be a
better solution, but it isn't backwards-compatible.)
Use List::Util::first instead of a homespun version.
Allow export of our new function.
Check if we got an allocation and an owner.
Merge pull request #81 from tmooney/find_result_for_variants_directory

Use the build directory to decide which result is the correct one.