13547: if an instance of KeepClient has an api_client object with the insecure

13547: if an instance of KeepClient has an api_client object with the insecure
flag set, and the ARVADOS_API_HOST_INSECURE environment variable is not set,
set the insecure flag on the KeepClient instance. Also set that flag on any
KeepService instances created by that KeepClient instance.

This makes arv-copy respect the ARVADOS_API_HOST_INSECURE value in the config
file(s) for the Arvados instances, when talking to keep proxy.

refs #13547

Arvados-DCO-1.1-Signed-off-by: Ward Vandewege <wvandewege@veritasgenetics.com>