Minor bugfix to IP::prettifyIP.

The offset returned by preg_match with the PREG_OFFSET_CAPTURE is an
absolute position in the string.  You shouldn't *add* it to the
current position in order to advance past the match.

Change-Id: I3631c34e02d9b830bf841bf960855626fbc88eb0
Merge "Minor bugfix to IP::prettifyIP."