get_feature_binary: Return const char*
get_feature_binary: Return const char*

There's no need to duplicate returned string. Well, it's expected
in one place, but I rather duplicate it there, because otherwise
we keep forgetting about freeing the returned value. Moreover,
the list of binaries is static.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

libvirt/libvirt-php,zippy2/libvirt-php,zippy2/libvirt-php,tucksaun/libvirt-php,libvirt/libvirt-php,tucksaun/libvirt-php,tucksaun/libvirt-php,zippy2/libvirt-php,libvirt/libvirt-php,tucksaun/libvirt-php