pimd: Avoid deleting SGRpt entry from PP->P state

pimd: Avoid deleting SGRpt entry from PP->P state

-Upon Receving SGRpt Prune message, transitioning from Prune Pending state
to NOINFO state, ifchannel entry was getting deleted in prune pending timer
expiry. This can result in SGRpt ifhchannel deleted and recreated upon receving
triggered or periodic SGRpt received from downstream.
The automation test failed as it expected (check) SGRpt entry at RP after it triggers
SPT switchover.

- While transitioning from Prune-Pending state to NOINFO(Pruned) state, Trigger
SGRpt message towards RP.

- Add/del some of the debug traces

Ticket:CM-16057
Reviewed By:CCR-6198
Testing Done:
Rerun test08 multiple times and observed passing it.

Pim-smoke with hardnode
Ran 95 tests in 11219.420s
FAILED (SKIP=10, failures=4)

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>