Bug 828: Fixed bug in NetUtils.isMulticastMACAddr() caused by sign extension.

This patch fixes a bug that returned false incorrectly when the MSB was set
in the MAC address.

Change-Id: I8d04534962b0a1a585cf0217969a6415f360140b
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>
(cherry picked from commit c1d6c147a5fdd6b18cf9f00e1bb7855020f2361f)
Merge "Bug 828: Fixed bug in NetUtils.isMulticastMACAddr() caused by sign extension." into stable/hydrogen