(maint) Test a different cert for extensions

The FOSS ssl/certificate_extensions test expects to be able to clear out
the ssl store and start again.  This is not feasible in PE; the solution
is to run the test against a differente certname.  Also leaving temp
dirs in place, because it makes it much easier to review the files that
were used when troubleshooting test failure.
Merge branch 'maint/stable/ssl-cert-ext-acceptance-fix-for-pe' into stable

* maint/stable/ssl-cert-ext-acceptance-fix-for-pe:
  (maint) Test a different cert for extensions