Move read/write handles in VMware drivers to OSLO

There is lot of common code between VMware drivers for nova and cinder;
for e.g., session management and VIM API invocation code. The new
VMware driver for glance and the telemetry agent for vSphere are also
planning to use this common code. This change moves the classes defining
read and write handles for image transfer between VMware servers and
image service into OSLO.

Change-Id: Idd5e0a3e13bb1e752ed577b63a012ca59c461bce
Implements: blueprint vmware-api
Merge "Move read/write handles in VMware drivers to OSLO"