Record hotplugged USB device in LXC live guest config

After hotplugging a USB device, the LXC driver forgot
to add the device def to the virDomainDefPtr.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
(cherry picked from commit a537827d)

Backport fixed for OOM error reporting

src/lxc/lxc_driver.c

@@ -3595,6 +3595,11 @@ lxcDomainAttachDeviceHostdevSubsysUSBLive(virLXCDriverPtr driver,
 
     mode = 0700 | S_IFCHR;
 
+    if (VIR_REALLOC_N(vm->def->hostdevs, vm->def->nhostdevs + 1) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
     if (virFileMakePath(dstdir) < 0) {
         virReportSystemError(errno,
                              _("Unable to create %s"), dstdir);
@@ -3620,6 +3625,8 @@ lxcDomainAttachDeviceHostdevSubsysUSBLive(virLXCDriverPtr driver,
                                 priv->cgroup) < 0)
         goto cleanup;
 
+    vm->def->hostdevs[vm->def->nhostdevs++] = def;
+
     ret = 0;
 
 cleanup: