Fix a bug in OkHostnameVerifier wildcard handling.

Wildcard domain name patterns of the form *.remainder are supposed to
match domain names that exactly match the remainder. Due to a bug,
the match was not exact but rather a prefix match: domain names
starting with the remainder would match too.

This CL fixes the issue.

Bug: 18432707
Change-Id: I2639ff51cabcbd395d4f30a9c69f9895738e0acf