collectd: add PACKAGECONFIG for libvirt, libesmtp

Add PACKAGECONFIG for libvirt, libesmtp to fix below warnings:

WARN: collectd: collectd rdepends on libvirt, but it isn't a build dependency?
WARN: collectd: collectd rdepends on libcrypto, but it isn't a build dependency?
WARN: collectd: collectd rdepends on libesmtp, but it isn't a build dependency?
WARN: collectd: collectd rdepends on libssl, but it isn't a build dependency?

Signed-off-by: Wenzong Fan <wenzong.fan@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>