BUG/MINOR: cfgparse: use the GLOBAL not LISTEN keywords list for spell checking

BUG/MINOR: cfgparse: use the GLOBAL not LISTEN keywords list for spell checking

In commit a0e8eb8ca ("MINOR: cfgparse: suggest correct spelling for
unknown words in global section") we got the ability to locate a better
matching word in case of error. But it mistakenly used the CFG_LISTEN
class of words instead of CFG_GLOBAL, resulting in proposing unsuitable
matches in addition to the long hard-coded list. Now, "tune.dh-param"
correctly proposes "tune.ssl.default-dh-param".

No backport is needed.