Fix remote_client param description

pkey param should accept private key and not public

Change-Id: Idbde6af7b574a045941edc92e7224bdd45f9df64
diff --git a/tempest/lib/common/utils/linux/remote_client.py b/tempest/lib/common/utils/linux/remote_client.py
index 224f3bf..d0cdc25 100644
--- a/tempest/lib/common/utils/linux/remote_client.py
+++ b/tempest/lib/common/utils/linux/remote_client.py
@@ -75,7 +75,7 @@
         :param ip_address: IP address to ssh to
         :param username: Ssh username
         :param password: Ssh password
-        :param pkey: Ssh public key
+        :param pkey: Ssh private key
         :param server: Server dict, used for debugging purposes
         :param servers_client: Servers client, used for debugging purposes
         :param ssh_timeout: Timeout in seconds to wait for the ssh banner