tests: Fix ssl-ciphers RO sb test with old openssl.

The test "read-only sb db:pssl access with ssl-ciphers and ssl-protocols"
fails when running with openssl which doesn't support some of passed
values.
For instance, on openssl 1.0.2 there is no support for 'SECLEVEL' and
test fails due to extra string in stderr, which is asserted as a part of
test:

  ./ovn.at:37851: ovn-sbctl --db=ssl:127.0.0.1:$TCP_PORT \
                    --private-key=$PKIDIR/testpki-test-privkey.pem \
                      --certificate=$PKIDIR/testpki-test-cert.pem \
                      --ca-cert=$PKIDIR/testpki-cacert.pem \
                      --ssl-ciphers='HIGH:!aNULL:!MD5:@SECLEVEL=1' \
                      --ssl-protocols='TLSv1,TLSv1.1,TLSv1.2' \
                    chassis-add ch vxlan 1.2.4.8
  --- - 2024-07-05 13:48:11.697647047 +0300
  +++ /builddir/build/BUILD/ovn-24.03.90/tests/testsuite.dir/at-groups/520/stderr 2024-07-05 13:48:11.694353357 +0300
  @@ -1,2 +1,3 @@
  +2024-07-05T10:48:11Z|00001|stream_ssl|ERR|SSL_CTX_set_cipher_list: error:140E6118:SSL routines:SSL_CIPHER_PROCESS_RULESTR:invalid command
   ovn-sbctl: transaction error: {"details":"insert operation not allowed when database server is in read only mode","error":"not allowed"}

This patch fixes the test adding grep of expected transaction error.

CC: Aliasgar Ginwala <aginwala@ebay.com>
Fixes: 620203f ("Fix segfault due to ssl-ciphers.")
Signed-off-by: Vladislav Odintsov <odivlad@gmail.com>
Acked-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Numan Siddique <numans@ovn.org>

tests/ovn.at

@@ -37854,9 +37854,9 @@ AT_CHECK([ovn-sbctl --db=ssl:127.0.0.1:$TCP_PORT \
                     --ca-cert=$PKIDIR/testpki-cacert.pem \
                     --ssl-ciphers='HIGH:!aNULL:!MD5:@SECLEVEL=1' \
                     --ssl-protocols='TLSv1,TLSv1.1,TLSv1.2' \
-                    chassis-add ch vxlan 1.2.4.8], [1], [ignore],
-[ovn-sbctl: transaction error: {"details":"insert operation not allowed when database server is in read only mode","error":"not allowed"}
-])
+                    chassis-add ch vxlan 1.2.4.8 2>&1 | grep 'transaction error]', [0], [dnl
+ovn-sbctl: transaction error: {"details":"insert operation not allowed when database server is in read only mode","error":"not allowed"}
+], [ignore])
 
 OVS_APP_EXIT_AND_WAIT([ovsdb-server])
 AT_CLEANUP