Plug memory leaks by explicitly freeing slurm_credential associated with

job, step, node, and partition info.
Add new function to free slurm_credential from RPC response.

src/common/slurm_protocol_api.c

@@ -908,6 +908,13 @@ void slurm_free_msg(slurm_msg_t * msg)
         xfree(msg);
 }
 
+/* 
+ * Free just the credential of a message
+ */
+void slurm_free_cred(void *cred)
+{
+        (void) g_slurm_auth_destroy(cred);
+}
 
 #if _DEBUG
 

src/common/slurm_protocol_api.h

@@ -426,4 +426,5 @@ int slurm_send_only_node_msg(slurm_msg_t * request_msg);
 
 /* Slurm message functions */
 void slurm_free_msg(slurm_msg_t * msg);
+void slurm_free_cred(void *cred);
 #endif