This commit fixes a crash reported as MDEV-28377 and a number
of other crashes in automated tests with mtr that are related
to broken .cnf files in galera and galera_3nodes suites, which
happened when automatically migrating MDEV-26171 from 10.3 to
subsequent higher versions.
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).
