Add support for SSL thumbprint when using FileWriteHandle
Add support for SSL thumbprint when using FileWriteHandle

When doing HTTP PUT to an ESX datastore clients often have SSL
thumbprint instead of CA certificate. This patch allows clients to
specify the thumbprint when using FileWriteHandle.

Change-Id: I3c360e90b5e96446904dfc89015a8ac9ad1c45d0

openstack/oslo.vmware