contexthubhal: fix result when hal doesn't send mgmt message to nanohub

Return an error when the hal thinks the app being started is already
running or when the app being unloaded/erased is either not running or
doesn't exist.

Bug: 118398281
Test: pass VtsHalContexthubV1_0
Change-Id: I9c5f884e11c86ba6a608c24614e41784d5d19308
Signed-off-by: Ben Fennema <fennema@google.com>