Don't use a fixed buffer for X509_NAME_oneline() in the client.
Do as the server does - allocate it dynamically.
For a test - regenerate certificates to have the server cert with
a long subject.
The problem is that the fix Bug#29784 was mistakenly
reverted when updating YaSSL to a newer version.
The solution is to re-apply the fix and this time
actually add a meaningful test case so that possible
regressions are caught.