heatclient : correct timeout parameter name
    
    The timeout parameter needs to be timeout_mins to match the
    engine API or the parameter will not be recognized by the
    engine.
    
    fixes bug 1129348
    
    Change-Id: I489364a2abed376f35bf2da24915db30c982e61b
    Signed-off-by: Steven Hardy <shardy@redhat.com>