Revert "ipv4: Fix incorrect route flushing when source address is deleted"

This reverts commit 2537b637 that
deleted the whole fib_tests.sh by mistake and caused fib_tests failure
in kselftests run.

Signed-off-by: Shaoying Xu <shaoyi@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>