Fix check of virKillProcess return status

The error code for virKillProcess is returned in the errno variable
not the return value. THis mistake caused the logs to be filled with
errors when shutting down QEMU processes

* src/qemu/qemu_process.c: Fix process kill check.

src/qemu/qemu_process.c

@@ -2518,7 +2518,6 @@ cleanup:
 void qemuProcessKill(virDomainObjPtr vm)
 {
     int i;
-    int rc;
     VIR_DEBUG("vm=%s pid=%d", vm->def->name, vm->pid);
 
     if (!virDomainObjIsActive(vm)) {
@@ -2540,9 +2539,8 @@ void qemuProcessKill(virDomainObjPtr vm)
         else
             signum = 0; /* Just check for existence */
 
-        rc = virKillProcess(vm->pid, signum);
-        if (rc < 0) {
-            if (rc != -ESRCH) {
+        if (virKillProcess(vm->pid, signum) < 0) {
+            if (errno != ESRCH) {
                 char ebuf[1024];
                 VIR_WARN("Failed to kill process %d %s",
                          vm->pid, virStrerror(errno, ebuf, sizeof ebuf));