qemu: don't use chardev FD passing with standalone args

When using domxml-to-native, we must generate CLI args that can be used
in a standalone scenario. This means no FD passing can be used. To
achieve this we must clear the QEMU_CAPS_CHARDEV_FD_PASS capability bit.
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

src/qemu/qemu_process.c

@@ -5124,6 +5124,9 @@ qemuProcessInit(virQEMUDriverPtr driver,
                                                       vm->def->os.machine)))
         goto cleanup;
 
+    if (flags & VIR_QEMU_PROCESS_START_STANDALONE)
+        virQEMUCapsClear(priv->qemuCaps, QEMU_CAPS_CHARDEV_FD_PASS);
+
     if (qemuDomainUpdateCPU(vm, updatedCPU, &origCPU) < 0)
         goto cleanup;
 
@@ -6632,6 +6635,8 @@ qemuProcessCreatePretendCmd(virQEMUDriverPtr driver,
 
     flags |= VIR_QEMU_PROCESS_START_PRETEND;
     flags |= VIR_QEMU_PROCESS_START_NEW;
+    if (standalone)
+        flags |= VIR_QEMU_PROCESS_START_STANDALONE;
 
     if (qemuProcessInit(driver, vm, NULL, QEMU_ASYNC_JOB_NONE,
                         !!migrateURI, flags) < 0)

src/qemu/qemu_process.h

@@ -81,6 +81,8 @@ typedef enum {
     VIR_QEMU_PROCESS_START_PRETEND      = 1 << 3,
     VIR_QEMU_PROCESS_START_NEW          = 1 << 4, /* internal, new VM is starting */
     VIR_QEMU_PROCESS_START_GEN_VMID     = 1 << 5, /* Generate a new VMID */
+    VIR_QEMU_PROCESS_START_STANDALONE   = 1 << 6, /* Require CLI args to be usable standalone,
+                                                     ie no FD passing and the like */
 } qemuProcessStartFlags;
 
 int qemuProcessStart(virConnectPtr conn,