qa/workunits/smb: add an argument to set up volume mappings

Add an argument to the cephadm shell wrapper function that
makes it easy and obvious where to add volume mappings.
This will be used in a future change to map in a directory
containing TLS certificates and such.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

qa/workunits/smb/tests/cephutil.py

@@ -56,6 +56,9 @@ def cephadm_shell_cmd(
         f'/home/{smb_cfg.ssh_user}/cephtest/cephadm',
         'shell',
     ]
+    volumes = kwargs.pop('volumes', [])
+    for v in volumes:
+        cmd.extend(['-v', v])
     cmd += list(args)
     proc = subprocess.run(cmd, **kwargs)
     if load is LoadJSON.BOTH: