zebra: Do not accept illegal safi's for route installation

zebra: Do not accept illegal safi's for route installation

The only two safi's that are usable for zebra for installation
of routes into the rib are SAFI_UNICAST and SAFI_MULTICAST.
The acceptance of other safi's is causing a memory leak:

Direct leak of 56 byte(s) in 1 object(s) allocated from:
    #0 0x5332f2 in calloc (/usr/lib/frr/zebra+0x5332f2)
    #1 0x7f594adc29db in qcalloc /opt/build/frr/lib/memory.c:110:27
    #2 0x686849 in zebra_vrf_get_table_with_table_id /opt/build/frr/zebra/zebra_vrf.c:390:11
    #3 0x65a245 in rib_add_multipath /opt/build/frr/zebra/zebra_rib.c:2591:10
    #4 0x7211bc in zread_route_add /opt/build/frr/zebra/zapi_msg.c:1616:8
    #5 0x73063c in zserv_handle_commands /opt/build/frr/zebra/zapi_msg.c:2682:2
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Sequence of events:

Upon vrf creation there is a zvrf->table[afi][safi] data structure
that tables are auto created for.  These tables only create SAFI_UNICAST
and SAFI_MULTICAST tables.  Since these are the only safi types that
are zebra can actually work on.  zvrf data structures also have a
zvrf->otable data structure that tracks in a RB tree other tables
that are created ( say you have routes stuck in any random table
in the 32bit route table space in linux ).  This data structure is
only used if the lookup in zvrf->table[afi][safi] fails.

After creation if we pass a route down from an upper level protocol
that has non unicast or multicast safi *but* has the actual
tableid of the vrf we are in, the initial lookup will always
return NULL leaving us to look in the otable.  This will create
a data structure to track this data.

If after this event you pass in a second route with the same
afi/safi/table_id, the otable will be created and attempted
to be stored, but the RB_TREE_UNIQ data structure when it sees
this will return the original otable returned and the lookup function
zebra_vrf_get_table_with_table_id will just drop the second otable.

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>