qa/rgw: renamed ssl task to openssl_keys

The ssl task located in a python file called `ssl.py` will generate
python module loading conflicts with the `ssl` system module, when
running QA tests using vstart_runner.py.

Signed-off-by: Ricardo Dias <rdias@suse.com>

qa/suites/rgw/verify/frontend/civetweb_ssl.yaml

@@ -1,5 +1,5 @@
 overrides:
-  ssl:
+  openssl_keys:
     root:
       client: client.0
       key-type: rsa:4096

qa/suites/rgw/verify/tasks/rgw_tests.yaml

@@ -5,7 +5,7 @@ tasks:
 - install:
     flavor: notcmalloc
 - ceph:
-- ssl:
+- openssl_keys:
 - rgw:
     client.0:
       valgrind: [--tool=memcheck]