Add python-midonetclient to the package's dependency

This patch adds python-midonetclient to the dependency of the
package created by fpm.

This fixes MN-2952.

Change-Id: I5e36456d512b5d71f010933f4b2498feba03fdfd
Signed-off-by: Taku Fukushima <tfukushima@midokura.com>