Reduce the time taken by NetUtil and DefaultChannelId class initialization

Motivation:

As reported in #2331, some query operations in NetworkInterface takes much longer time than we expected.  For example, specifying -Djava.net.preferIPv4Stack=true option in Window increases the execution time by more than 4 times.  Some Windows systems have more than 20 network interfaces, and this problem gets bigger as the number of unused (virtual) NICs increases.

Modification:

Use NetworkInterface.getInetAddresses() wherever possible.
Before iterating over all NICs reported by NetworkInterface, filter the NICs without proper InetAddresses.  This reduces the number of candidates quite a lot.
NetUtil does not query hardware address of NIC in the first place but uses InetAddress.isLoopbackAddress().
Do not call unnecessary query operations on NetworkInterface.  Just get hardware address and compare.

Result:

Significantly reduced class initialization time, which should fix #2331.
Prefer the NIC with global IP address when getting the default machine ID

Motivation:

When there are two MAC addresses which are good enough, we can choose the one with better IP address rather than just choosing the first appeared one.

Modification:

Replace isBetterAddress() with compareAddresses() to make it return if both addresses are in the same preference level.
Add compareAddresses() which compare InetAddresses and use it when compareAddress(byte[], byte[]) returns 0 (same preference)

Result:

More correct primary MAC address detection
Use the length of MAC address as the last property to compare to get the best MAC address

Motivation:

Some operating systems like Windows 7 uses a valid globally unique EUI-64 MAC address for a virtual device (e.g. 00:00:00:00:00:00:00:E0), and because it's usually longer than the legit MAC-48 address, we should not use the length of MAC address when two MAC addresses are of the same quality.  Instead, we should compare the INET address of the NICs before comparing the length of the MAC addresses.

Modification:

Compare the length of MAC addresses as a last resort.

Result:

Correct MAC address detection in Windows with IPv6 enabled.