Fix leftover typo '&' -> '&&'

Fix leftover typo '&' -> '&&'

The actual origin of this so called typo are two commits.  The first one
was commit 72f8a7f that came up with the following condition:

if ((i == 8) & (flags & VIR_QEMU_PROCESS_KILL_FORCE))

Fortunately this succeeded thanks to bool being (int)1 and
VIR_QEMU_PROCESS_KILL_FORCE having the value of 1 << 0.  The check was
then moved and altered in 8fd38231179c394f07d8a26bcbf3a0faa5eeaf24 to
current state:

if ((i == 50) & force)

that will work again (both sides of '&' being booleans), but since this
was missed so many times, it may pose a problem in the future in case it
gets copy-pasted again.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>