[MINOR][BUILD] Add distdir to fileset ofmaven-clean-plugin

[LuciferYang]

What changes were proposed in this pull request?

This pr add add dist to fileset ofmaven-clean-plugin to make mvn clean can delete the dist dir which created by dev/make-distribution.sh.

Why are the changes needed?

dev/make-distribution.sh will create a dist dir but no one cleaned it up.

Does this PR introduce any user-facing change?

No

How was this patch tested?

Local test to confirm that dist dir can be cleaned

[LuciferYang]

or should we add rm -rf "$DISTDIR" after line 291?

spark/dev/make-distribution.sh

Lines 284 to 292 in 790a697

	if [ "$MAKE_TGZ" == "true" ]; then
	TARDIR_NAME=spark-$VERSION-bin-$NAME
	TARDIR="$SPARK_HOME/$TARDIR_NAME"
	rm -rf "$TARDIR"
	cp -r "$DISTDIR" "$TARDIR"
	tar czf "spark-$VERSION-bin-$NAME.tgz" -C "$SPARK_HOME" "$TARDIR_NAME"
	rm -rf "$TARDIR"
	fi

[srowen]

Merged to master

[LuciferYang]

thanks @srowen