[MINOR] cfgparse: fix off-by 2 in error message size

was just looking through the source, and noticed this... :)
(cherry picked from commit 63b76be713784f487e8d0c859a85513642fe7bdc)
(cherry picked from commit a801db6c5ea750f93a3795dbb2e70c03e05bbef4)
1 file changed