Use InetAddresses.forString instead of InetAddress.getByName

Use InetAddresses.forString instead of InetAddress.getByName

Unlike InetAddress.getByName(), Guava's InetAddresses.forString()
never cause DNS services to be accessed.
JDK equivalents whenever you are expecting to handle only IP address string literals,
so there is no blocking DNS penalty for a malformed string.

See:
https://google.github.io/guava/releases/22.0/api/docs/com/google/common/net/InetAddresses.html#forString-java.lang.String-

Change-Id: Id1fc5fa45465b0e0b3aea7d60b9fdb855240d902
Signed-off-by: Marek Gradzki <mgradzki@cisco.com>