Fix CLEANUP/KEEPLOG not working when set to NO.

Before this patch, they were conditionally unset before
the code checking for the presence of all the required
configuration variables.
While at it, clean up the code a little.

Signed-off-by: Mauro Giachero <mauro.giachero@gmail.com>

src/usr/sbin/sbopkg

@@ -111,20 +111,11 @@ config_check() {
         echo "$SCRIPT: No $SBOPKG_CONF or ~/.sbopkg.conf was found." 1>&2
         echo "Please create at least one of them and run $SCRIPT again." 1>&2
         exit 1
-    else
+    fi
+
     [[ -e $SBOPKG_CONF ]] && . $SBOPKG_CONF
     [[ -e $HOME/.sbopkg.conf ]] && . $HOME/.sbopkg.conf
 
-        if [[ $KEEPLOG == [Yy][Ee][Ss] ]]; then
-            KEEPLOG=1
-        else
-            unset KEEPLOG
-        fi
-        if [[ $CLEANUP == [Yy][Ee][Ss] ]]; then
-            CLEANUP=1
-        else
-            unset CLEANUP
-        fi
     # Some configuration options are mandatory
     for VAR in REPO_ROOT LOGDIR QUEUEDIR SRCDIR SBOPKGTMP REPO_NAME \
         REPO_BRANCH KEEPLOG CLEANUP LOGFILE DEBUG TMP OUTPUT RSYNCFLAGS \
@@ -155,6 +146,13 @@ EOF
         echo "The \$DEBUG variable must be set to 0, 1, or 2." 1>&2
         exit 1
     fi
+
+    # Convert some YES/NO variables into 'set/unset' ones.
+    if [[ $KEEPLOG == [Nn][Oo] ]]; then
+        unset KEEPLOG
+    fi
+    if [[ $CLEANUP == [Nn][Oo] ]]; then
+        unset CLEANUP
     fi
 
     # Make sure there are no unexpected files in $SBOPKGTMP