pimd, pim6d: Don't configure link-local, Multicast, Unspecified address as RP

pimd, pim6d: Don't configure link-local, Multicast, Unspecified address as RP

Problem:
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frr(config)# do show ipv6 pim interface
 Interface  State  Address                   PIM Nbrs  PIM DR  FHR  IfChannels
 ens192     up     fe80::250:56ff:feb7:3619  0         local   0    1

Configure ens192 interface link-local address as RP.
frr(config)# ipv6 pim rp fe80::250:56ff:feb7:3619
No Path to RP address specified: fe80::250:56ff:feb7:3619

frr(config)# do show ipv6 pim rp-info
 RP address                group/prefix-list  OIF      I am RP  Source  Group-Type
 fe80::250:56ff:feb7:3619  ff00::/8           Unknown  yes      Static  ASM

Fix:
===
RP should not be link-local, multicast and unspecified address.

Signed-off-by: Sarita Patra <saritap@vmware.com>