zebra: Reorg struct route_entry to have important bits first

[donaldsharp]

The struct route_entry had items that were almost never used at the front of the data structure resulting in items that would be loaded first into memory that were never used. Let's reorg a tiny bit and put all the frequently used items in the first cache line. I'm sure people will notice .000000001 speedup

new layout:

sharpd@eva /w/h/s/frr1 (reorg_route_entry)> /home/sharpd/pahole/build/pahole --reorganize --show_reorg_steps -C route_entry zebra/.libs/zebra struct route_entry {
struct re_list_item next; /* 0 8 /
struct nhg_hash_entry * nhe; / 8 8 /
uint32_t nhe_id; / 16 4 /
uint32_t nhe_installed_id; / 20 4 /
int type; / 24 4 /
vrf_id_t vrf_id; / 28 4 /
uint32_t table; / 32 4 /
uint32_t metric; / 36 4 /
uint32_t mtu; / 40 4 /
uint32_t nexthop_mtu; / 44 4 /
uint32_t flags; / 48 4 /
uint32_t status; / 52 4 /
uint32_t dplane_sequence; / 56 4 /
uint16_t instance; / 60 2 /
uint8_t distance; / 62 1 */

/* XXX 1 byte hole, try to pack */

/* --- cacheline 1 boundary (64 bytes) --- */
route_tag_t                tag;                  /*    64     4 */

/* XXX 4 bytes hole, try to pack */

time_t                     uptime;               /*    72     8 */
struct re_opaque *         opaque;               /*    80     8 */
struct nexthop_group       fib_ng;               /*    88    32 */
struct nexthop_group       fib_backup_ng;        /*   120    32 */

/* size: 152, cachelines: 3, members: 20 */
/* sum members: 147, holes: 2, sum holes: 5 */
/* last cacheline: 24 bytes */

};