Treat ENOMSG as TRY_AGAIN.

ENOMSG is returned by the ringbuffer when you attempt to read
a message and there is nothing there to read.

Signed-off-by: Angus Salkeld <asalkeld@redhat.com>
Reviewed-by: Steven Dake <sdake@redhat.com>

common_lib/error_conversion.c

@@ -52,6 +52,7 @@ cs_error_t qb_to_cs_error (int result)
 	case ENOMEM:
 		err = CS_ERR_NO_MEMORY;
 		break;
+	case ENOMSG:
 	case ENOBUFS:
 	case ETIMEDOUT:
 	case EAGAIN: