Fixed PHP-1102: php driver throws exception when connect string contains an unresolvable
hostname

If we have any usable connection we should make sure we don't throw an exception and bork.
Unfortunately this means that letting the user know that his connection string is very bad
is difficult and only discoverable through MongoLog - unless the entire seed list is
broken
Add test for only invalid-hostname in seedlist
Fix test title as per PR CR
Merge pull request #701 from bjori/PHP-1102-exception-throwing

Fixed PHP-1102: PHP driver throws exception when connect string contains an un-resolvable hostname

* bjori/PHP-1102-exception-throwing:
  Fix test title as per PR CR
  Add test for only invalid-hostname in seedlist
  Fixed PHP-1102: php driver throws exception when connect string contains an unresolvable hostname
Merge branch 'v1.5'

* v1.5:
  Fix test title as per PR CR
  Add test for only invalid-hostname in seedlist
  Fixed PHP-1102: php driver throws exception when connect string contains an unresolvable hostname