macos: fix growlagent icon handling

macos: fix growlagent icon handling

the whole of the api used for icon handling when you steal it
from a resource fork is deprecated in new macos. fine. we'll just make
an app bundle by cheating, move andy into a standalone icns file,
install him into the "bundle" and open it the macos way.

Change-Id: I94b3fdb5fdb08b28400bd0f6f6a18a07840124df
Reviewed-on: http://gerrit.openafs.org/7786
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>