pimd: fixup JD macro to use "peer-msdp-sa" check instead of I_am_RP check

pimd: fixup JD macro to use "peer-msdp-sa" check instead of I_am_RP check

JD macro is defined by the RFC as -
bool JoinDesired(S,G) {
    return (immediate_olist(S,G) != NULL
        OR (KeepaliveTimer(S,G) is running
        AND inherited_olist(S,G) != NULL))
}

However for MSDP synced SA the KAT will not be running so an exception is
needed. Earlier I had done this by relaxing KAT_run requirements entirely
on the RP. However as that prevents the source from being aged out in some
cases I have made the check more narrow i.e. has to an MSDP peer added
entry.

Ticket: CM-24398

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>