Don't link virt-login-shell against libvirt.so (CVE-2013-4400)

Don't link virt-login-shell against libvirt.so (CVE-2013-4400)

The libvirt.so library has far too many library deps to allow
linking against it from setuid programs. Those libraries can
do stuff in __attribute__((constructor) functions which is
not setuid safe.

The virt-login-shell needs to link directly against individual
files that it uses, with all library deps turned off except
for libxml2 and libselinux.

Create a libvirt-setuid-rpc-client.la library which is linked
to by virt-login-shell. A config-post.h file allows this library
to disable all external deps except libselinux and libxml2.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>