Fix compatibility with older confirm_resize() calls

Commit ff4194bec79067bf77ab25caec1e40ad3709ea07 bumped the RPC
version and format for compute_confirm_resize() without providing
compatibility with older installations. This patch converts it
to a instance-dict style of primitive before sending it, if we're
pinned to an older version.

Change-Id: Ic631b70c005bfd0efe6965ad024890cc2caf947c
Merge "Fix compatibility with older confirm_resize() calls"