tests: Fix random failure in test_PIM_hello_tx_rx_p1

tests: Fix random failure in test_PIM_hello_tx_rx_p1

The test case test_PIM_hello_tx_rx_p1 is failing randomly because
sometimes the hello packet is received and sometimes not received while getting
the stats data.
When the hello packet is received HelloRx gets incremented to 1 and then
shutdown of the interface is executed which resets the stats to 0
and again when "no shutdown" of the interface is done, the stats get incremented to 1.
The test case checks after "no shutdown" of the interface whether the stats is incremented
but in this case although the stats got incremented the before and after value is same.
Hence the test case failed.

Adding correct expectations in the test case.

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