Remove the superfluous call to _rtld_error() in symlook_default().

The function's callers generate the error message when appropriate.

This eliminates the message ``Undefined symbol "__register_frame_info"''
which was bogusly returned by dlerror() in some cases.

libexec/rtld-elf/rtld.c

@@ -1831,8 +1831,6 @@ symlook_default(const char *name, unsigned long hash,
 
     if (def != NULL)
 	*defobj_out = defobj;
-    else
-	_rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
     return def;
 }