scripts/rpc: add try-except around call_rpc_func

Missing try-except block around call_rpc_func().
If called function returned error there was an uncaught exception
which resulted in backtrace printed to screen.

Change-Id: Ifb37c29d70b93ef648a0503643a51cc1967ef8d0
Signed-off-by: Karol Latecki <karol.latecki@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/456956
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>

scripts/rpc.py

@@ -1826,7 +1826,11 @@ Format: 'user:u1 secret:s1 muser:mu1 msecret:ms1,user:u2 secret:s2 muser:mu2 mse
     args = parser.parse_args()
     args.client = rpc.client.JSONRPCClient(args.server_addr, args.port, args.timeout, log_level=getattr(logging, args.verbose.upper()))
     if hasattr(args, 'func'):
-        call_rpc_func(args)
+        try:
+            call_rpc_func(args)
+        except JSONRPCException as ex:
+            print(ex)
+            exit(1)
     elif sys.stdin.isatty():
         # No arguments and no data piped through stdin
         parser.print_help()