node_device_udev: Serialize access to pci_get_strings)_

node_device_udev: Serialize access to pci_get_strings)_

Since the functions provided by libpciaccess are not thread-safe,
when the udev-event and nodedev-init threads of libvirt call the
pci_get_strings function provided by libpaciaccess at the same
time the following can happen:

nodedev-init thread:
nodeStateInitializeEnumerate ->
  udevEnumerateDevices->
    udevProcessDeviceListEntry ->
      udevAddOneDevice ->
        udevGetDeviceDetails->
          udevProcessPCI ->
            udevTranslatePCIIds ->
              pci_get_strings -> (libpciaccess)
                find_device_name ->
                  populate_vendor ->
                    d = realloc( vend->devices, (vend->num_devices + 1), * sizeof( struct pci_device_leaf ) );
                    vend->num_devices++;

udev-event thread:
udevEventHandleThread ->
  udevHandleOneDevice ->
    udevAddOneDevice->
      udevGetDeviceDetails->
        udevProcessPCI ->
          udevTranslatePCIIds ->
            pci_get_strings -> (libpciaccess)
              find_device_name ->
                populate_vendor ->
                  d = realloc( vend->devices, (vend->num_devices + 1), * sizeof( struct pci_device_leaf ) );
                  vend->num_devices++;

Signed-off-by: WangJian <wangjian161@huawei.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>