CA-152343: Start SMAPIv1 proxies later in the startup sequence

On a slave this requires making a DB call to the master to find out
which SM objects exist, so this needs to be done after starting HA (if
applicable) and setting up the database connection to the master.

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #2056 from johnelse/ca-152343

CA-152343: Start SMAPIv1 proxies later in the startup sequence
import_raw_vdi: Pass Content-Length to vhd-tool

This passes the `Content-Length` header to `vhd-tool serve` when using
raw non-chunked imports. This way clients don't need to manually pad out
the HTTP PUT with zeros, to fill it up to the next 2MB boundary.
Merge pull request #2063 from chengsun/fix-import-raw-vdi

import_raw_vdi: Pass Content-Length to vhd-tool