MDEV-27181: Galera SST scripts should use ssl_capath for CA directory

1. Galera SST scripts should use ssl_capath (not ssl_ca) for CA
   directory. The current implementation tries to automatically
   detect the path using the trailing slash in the ssl_ca variable
   value, but this approach is not compatible with the server
   configuration. Now, by analogy with the server, SST scripts
   also use a separate ssl_capath variable. In addition, a similar
   tcapath variable has been added for the old-style configuration
   (in the "sst" section).
2. Openssl utility detection made more reliable.
3. Removed extra spaces in automatically generated command lines -
   to simplify debugging of the SST scripts.
4. In general, the code for detecting the presence or absence of
   auxiliary utilities has been improved - it is made more reliable
   in some configurations (and for shells other than bash).

mysql-test/std_data/capath/ed1f42db.0

@@ -0,0 +1 @@
+cacert.pem