cloudstack api post and ssl fix

Signed-off-by: Sebastien Goasguen <runseb@gmail.com>
rbd: Use qemu-img to convert from QCOW2 templates to RBD directly.

This saves the step of writing to a temporary image in /tmp first before
writing to RBD.

This is possible due to a new version in librbd. With the rbd_default_format
setting we can now force qemu-img to create format 2 RBD images.

This is available since Ceph version 0.67.5 (Dumpling).