tests: Fix for test_pim_dr_nondr_with_ospf_topo2 test failure

tests: Fix for test_pim_dr_nondr_with_ospf_topo2 test failure

This test is failing intermittently because sometimes igmp
local join is not getting deleted. I did split the joins means
trying to delete igmp local joins one by one. I tried running
tests multiple times and it seems to be working fine with
current changes.

There was an issue found during debugging this test failure,
which was raised already:
Issue# https://github.com/FRRouting/frr/issues/11105

Signed-off-by: Kuldeep Kashyap <kashyapk@vmware.com>