ospfd: ospf routing table update upon Changing area from normal to nssa

ospfd: ospf routing table update upon Changing area from normal to nssa

Description:
	When changing the area from normal to NSSA, previous area's
	ASBR router's type-5 also calculated and added to routing table along
	with Type-7 lsas.
	Made a change in route calculation such that it will not consider Type-5
	lsas in calculation if it is originated from NSSA ASBR router.
	These lsas will be age out at MAX age.

  log:
  frr(config-router)# do show ip route
	Codes: K - kernel route, C - connected, S - static, R - RIP,
         O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
         T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
         f - OpenFabric,
         > - selected route, * - FIB route, q - queued, r - rejected, b - backup
         t - trapped, o - offload failure

	K>* 0.0.0.0/0 [0/0] via 10.112.157.253, ens160, 00:32:47
	C>* 10.112.156.0/23 is directly connected, ens160, 00:32:47
	S>* 22.22.22.2/32 [1/0] is directly connected, ens192, weight 1, 00:20:03
	O>* 33.33.33.0/24 [110/20] via 100.1.1.220, ens192, weight 1, 00:08:55
				   via 100.1.1.220, ens192, weight 1, 00:08:55
	O   100.1.1.0/24 [110/10] is directly connected, ens192, weight 1, 00:21:32
	C>* 100.1.1.0/24 is directly connected, ens192, 00:23:11
  frr(config-router)# do show ip ospf  route
	============ OSPF network routing table ============
	N    100.1.1.0/24          [10] area: 0.0.0.1
                           directly attached to ens192

	============ OSPF router routing table =============
	R    2.2.2.2               [10] area: 0.0.0.1, ASBR
                           via 100.1.1.220, ens192

	============ OSPF external routing table ===========
	N E2 33.33.33.0/24         [10/20] tag: 0
                           via 100.1.1.220, ens192
                           via 100.1.1.220, ens192

Signed-off-by: Rajesh Girada <rgirada@vmware.com>