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

The actual origin of this so called typo are two commits.  The first one
was commit 72f8a7f1 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 8fd38231 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: NMartin Kletzander <mkletzan@redhat.com>

src/util/virprocess.c

@@ -354,7 +354,7 @@ virProcessKillPainfully(pid_t pid, bool force)
         int signum;
         if (i == 0) {
             signum = SIGTERM; /* kindly suggest it should exit */
-        } else if ((i == 50) & force) {
+        } else if (i == 50 && force) {
             VIR_DEBUG("Timed out waiting after SIGTERM to process %lld, "
                       "sending SIGKILL", (long long)pid);
             /* No SIGKILL kill on Win32 ! Use SIGABRT instead which our