Fixed flaws with overly strict or, conversely,
overly soft verification of certificates in some
scenarios:

1. Removed the check that the 'commonname' (CN) in the
   certificate matches the 'localhost' value on the side
   of the joiner node, which was performed earlier, even
   if the address was received by the script only as an
   argument (out of the exchange via the Galera protocol) -
   since for the joining node this argument always contains
   its own local address, not the address of the remote host,
   so it is always treated as 'localhost', which is not
   necessarily true (outside of mtr testing);
2. Removed checking the domain name or IP-address of the
   peer node in the encrypt=2 mode;
3. Fixed checking of compliance of certificates when
   rsync SST is used;
4. Added the ability to specify CA not only as a file,
   but also as a path to the directory where the certificates
   are stored. To do this, the user just needs to specify the
   path to this directory as the value ssl-ca or tca parameter,
   ending with the '/' character.