bug: weak constraint of ipv4 and incorrect code logic in hostname_from_ip

[Smityz]

rdsn/src/core/core/utils.cpp

Line 116 in 07f2e65

if (!addr.from_string_ipv4(ip_port)) {

addr.from_string_ipv4 is too weak to limit the ipv4 address, it only judges by the format of addresses, and don't care about if its value valid. So this function can't limit ip address like 123.456.789.123

rdsn/src/core/core/utils.cpp

Line 130 in 07f2e65

if (address.type() != HOST_TYPE_IPV4) {

rdsn/src/core/tests/hostname_test.cpp

Line 40 in ca49482

ASSERT_FALSE(dsn::utils::hostname(rpc_example_failed, &hostname_result));

This unit test should not be done like this,address.type() != HOST_TYPE_IPV4 can't tell if its value valid, because address.type has been assigned before it was passed in.

[neverchanje]

What condition does our from_string_ipv4 make a problem?