[Password Manager] Prevent error logging for old LoginDatabase entries

The logging was meant to fire when there was a problem with the serialized
format, not when an old entries was being deserialized.

BUG=344180

Review URL: https://codereview.chromium.org/182263005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256111 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256111