Add resize_server in compute.base

This is to add a common function resize_server in compute.base,
to accomplish the procedure of resize and confirm resize until
finally the server becomes ACTIVE. This procedure appears in
several testcases and so can be simplified by using the common
function.

Change-Id: I6661d3415b4b183d785f05301dcbdd3e63fb51b9
3 files changed