netd: reorder the operations in getRouteTableForInterfaceLocked.

when network was switched quickly between wifi and cellular,
netd should always use old ifindex to delete ip rule/route,
and new ifindex to add ip rule/route.

BUG: 128805131
Test: built, booted, datausage, Phone call, Internet under
wifi and cellular data
Change-Id: I2d88709a00d50e318b02362ffac543a1e7e40a81