honor libpod.conf in /usr/share/containers
we should be looking for the libpod.conf file in /usr/share/containers
and not in /usr/local.  packages of podman should drop the default
libpod.conf in /usr/share.  the override remains /etc/containers/ as
well.
Fixes:
@@ -52,7 +52,7 @@ const (
var (
// InstallPrefix is the prefix where podman will be installed.
// It can be overridden at build time.
- installPrefix = "/usr/local"
+ installPrefix = "/usr"
// EtcDir is the sysconfdir where podman should look for system config files.
// It can be overridden at build time.
etcDir = "/etc"
