zebra: Convert label processing to Meta-Q

zebra: Convert label processing to Meta-Q

Convert label processing that comes from zapi messages
into being handled by the meta-Q.  This is because early
route processing is going to be moved to the meta-Q as
well and we will have a chicken and egg problem without
moving this code to be processed by the meta-Q.

Ordering of messages from ospf as an example:
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:48] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:48] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:48] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:48] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:62] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:43] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:61] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_ROUTE_ADD:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_MPLS_LABELS_REPLACE:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_MPLS_LABELS_REPLACE:0:66] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_MPLS_LABELS_REPLACE:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_MPLS_LABELS_REPLACE:0:47] comes from socket [36]
2022/08/09 08:55:52.740 ZEBRA: [YXG8K-BCYMV] zebra message[ZEBRA_MPLS_LABELS_REPLACE:0:47] comes from socket [36]

The ZEBRA_MPLS_LABELS_REPLACE immediately turn around and attempt to replace nexthop labels on routes that
were added.  If the route add is placed on the metaQ, it will not exist yet and as such the label replace
will fail.

Modify the zebra code to take the label operations and place them on the metaQ as well.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>