attrs in tool_server_controls() used uninitialized (ITS#2728)

[h.b.furuseth@usit.uio.no]

Full_Name: Hallvard B Furuseth
Version: HEAD
OS: 
URL: 
Submission from: (NULL) (129.240.186.42)
Submitted by: hallvard


In clients/tools/common.c:tool_server_controls(),
if preread or postread is set,
'attrs' is used unconditionally but only set if
'preread_attrs' is true.