doc: doc build errors not being reported

PR #3665 moved all the doc build artifacts into the _build folder and
updated scripts and Makefile to account for this, except missed a fix in
the script that checks for known issues. This patch fixes that but shows
we've got a bunch of issues that have not been being reported so we'll
need to fix those problems to resolve failing doc builds.

Also fixed process of the VERSION file in conf.py since the path to that
file was changed by PR #3665 as well and was raising an exeception that
was being masked.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>

doc/scripts/filter-doc-log.sh

@@ -31,13 +31,13 @@ fi
 
 if [ -s "${LOG_FILE}" ]; then
    $KI_SCRIPT --config-dir ${CONFIG_DIR} ${LOG_FILE} > ${BUILDDIR}/doc.warnings 2>&1
-   if [ -s doc.warnings ]; then
+   if [ -s ${BUILDDIR}/doc.warnings ]; then
 	   echo
 	   echo -e "${red}New errors/warnings found, please fix them:"
 	   echo -e "=============================================="
 	   $TPUT sgr0
 	   echo
-	   cat doc.warnings
+	   cat ${BUILDDIR}/doc.warnings
 	   echo
 	   exit 1
    else