Fix off-by-one bug when parsing MySQL EOF packet. Fixes #2128

CHANGELOG

@@ -3,6 +3,9 @@
 o [NSE][GH#2136][GH#2137] Rectify error "time result cannot be represented..."
   in the AFP library. [Clément Notin]
 
+o [NSE][GH#2128] MySQL library was not properly parsing server responses,
+  resulting in script crashes. [nnposter]
+
 o [NSE] Script mysql-audit now defaults to the bundled mysql-cis.audit for
   the audit rule base. [nnposter]
 

nselib/mysql.lua

@@ -384,7 +384,7 @@ function decodeQueryResponse( socket )
         -- Is this the EOF packet?
         if b == EOF_MARKER then
           -- we don't want the EOF Packet included
-          block_end = pos - HEADER_SIZE
+          block_end = pos - HEADER_SIZE - 1
           pos = pos + header.len
           break
         end