build: install libvirt sysctl file correctly

build: install libvirt sysctl file correctly

https://bugzilla.redhat.com/show_bug.cgi?id=887017 reports that
even though libvirt attempts to set fs.aio-max-nr via sysctl,
the file was installed with the wrong name and gets ignored by
sysctl.  Furthermore, 'man systcl.d' recommends that packages
install into hard-coded /usr/lib/sysctl.d (even when libdir is
/usr/lib64), so that sysadmins can use /etc/sysctl.d for overrides.

* daemon/Makefile.am (install-sysctl, uninstall-sysctl): Use
correct location.
* libvirt.spec.in (network_files): Reflect this.