pimd: fixup join desired handling to match the RFC defined macro

pimd: fixup join desired handling to match the RFC defined macro

This commit includes the following changes -
1. kat needs to be included when evaluting join desired on a (S,G)
   entry.
2. there were cases where we were adding OIF based on joindesired
   being true for unrelated reasons (on other OIFs). cleaned up those
   cases.
3. make all calls to pim_upstream_switch conditional on the JoinDesired
   macro.

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