Deprecate libcros CryptohomeAsyncSetOwnerUser

This deprecates the CryptohomeAsyncSetOwnerUser method in libcros obsoleted
by the switch of cryptohomed to libpolicy.

BUG=chromium-os:25464
TEST=built chrome and libcros
CQ-DEPEND=I2c085b927fd5412edf02f9026cad5dd7fc608ccc

Change-Id: I0236456756cd136b505260a08ebce9bb2f429b7a
Reviewed-on: https://gerrit.chromium.org/gerrit/14947
Commit-Ready: Bartosz Fabianowski <bartfab@google.com>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Tested-by: Bartosz Fabianowski <bartfab@google.com>
4 files changed