Add 'icehouse-compat' to [upgrade_levels] compute=

Add support for the 'icehouse-compat' value for the compute
configuration option in the [upgrade_levels] configuration option group.
This option is set during a live upgrade from havana to icehouse to
ensure that compute messages are sent that both havana and icehouse
understand.

This is added to stable/havana in this change id:
If09bd38c9d8c3beb5b95107c497699dec47aa3ef

DocImpact

Change-Id: Ic6656457afced20bff2f23c03493e72a96a00fb9
Merge "Add 'icehouse-compat' to [upgrade_levels] compute="