pimd: During prune pending, behave as NOINFO state

pimd: During prune pending, behave as NOINFO state

Fixed ANVL Conformance PIM-SM 16.3 test case.

When (S,G,rpt) prune is received, we were installing
the mroute immediately with none as OIF.
This leads to dropping the (S,G) traffic during prune
pending time as well.

Also we should not install the mroute if there is no
change in the rpf update.

These 2 things lead to the failure of the test case.

Fixed it by blocking the installation in this scenario.
When prune pending timer pops, it will take care of
installing the mroute with  none as OIF.

Fixes: #11535
Signed-off-by: Mobashshera Rasool <mrasool@vmware.com>