Set the string-mask to utf8only

If subject had utf-8 characters in them, the encoding chosen by OpenSSL for
defaults T61.

From the OpenSSL source code:
	 * utf8only : only use UTF8Strings (RFC2459 recommendation for 2004).

That was 10 years ago, and the last remnant that had problems with it
was Netscape, which is no longer a problem.

A request changes from:
   13:d=5  hl=2 l=   3 prim: OBJECT            :commonName
   18:d=5  hl=2 l=   9 prim: T61STRING         :Gurka ���

To:
   13:d=5  hl=2 l=   3 prim: OBJECT            :commonName
   18:d=5  hl=2 l=  12 prim: UTF8STRING        :Gurka åäö