Likewise, given if (foo != NULL) free (foo); remove the useless "if" test.

* proxy/libvirt_proxy.c: Remove unnecessary "if" test before free.
* python/generator.py: Likewise.
* qemud/qemud.c: Likewise.
* src/buf.c: Likewise.
* src/conf.c: Likewise.
* src/hash.c: Likewise.
* src/iptables.c: Likewise.
* src/libvirt.c: Likewise.
* src/openvz_conf.c: Likewise.
* src/qemu_conf.c: Likewise.
* src/qemu_driver.c: Likewise.
* src/remote_internal.c: Likewise.
* src/test.c: Likewise.
* src/virsh.c: Likewise.
* src/virterror.c: Likewise.
* src/xen_internal.c: Likewise.
* src/xen_unified.c: Likewise.
* src/xend_internal.c: Likewise.
* src/xm_internal.c: Likewise.
* src/xml.c: Likewise.
* src/xmlrpc.c: Likewise.
* src/xs_internal.c: Likewise.
* tests/testutils.c: Likewise.
* tests/xencapstest.c: Likewise.
* tests/xmconfigtest.c: Likewise.