build: Link security manager into libvirt.so

build: Link security manager into libvirt.so

Security manager is not a dynamically loadable driver, it's a common
infrastructure similar to util, conf, cpu, etc. used by individual
drivers. Such code is allowed to be linked into libvirt.so.

This reverts commit ec5b7bd2ecbf40ceff5b2d4fc00d5cfdfba966a4 and most of
aae5cfb69948fddef556f8f5b9f80a444f9c6125.

This patch is supposed to fix virdrivermoduletest failures for qemu and
lxc drivers as well as libvirtd's ability to load qemu and lxc drivers.