sdk: Add X-Ovirt-Expect and Expect

The HTTP Expect header is rejected by the Apache web server if its
values is anythiong other than 100-continue. To avoid problems the
engine explicitly removes it, and it accepts an alternative
X-Ovirt-Except header, with the same values and semantics. This patch
changes the SDK so that it will automatically add the alternative header
when the user adds the original one.

Change-Id: I2216c2256699d81dbb1a553177af39bb6a42fb3d
Related: https://bugzilla.redhat.com/1093784
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>