qemu_process: Fix theoretical overflow in uint to bool typecast
qemu_process: Fix theoretical overflow in uint to bool typecast

The qemuPrepareNVRAM() function accepts three arguments and the
last one being a boolean type. However, when the function is
called from qemuProcessPrepareHost() the argument passed is a
result of logical and of @flags (unsigned int) and
VIR_QEMU_PROCESS_START_RESET_NVRAM value. In theory this is
unsafe to do because if the value of the flag is ever changed
then this expression might overflow. Do what we do elsewhere:
double negation.

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

libvirt/libvirt,libvirt/libvirt,jfehlig/libvirt,zippy2/libvirt,crobinso/libvirt,crobinso/libvirt,jfehlig/libvirt,zippy2/libvirt,jfehlig/libvirt,crobinso/libvirt,jfehlig/libvirt,crobinso/libvirt,olafhering/libvirt,olafhering/libvirt,olafhering/libvirt,zippy2/libvirt,libvirt/libvirt,zippy2/libvirt,olafhering/libvirt,libvirt/libvirt