dist-docs: Include manpages generated from rST.

Some manpages are generated from rST, but these are not included
in 'dist-docs' make target.

Fixes: fd0837a ("doc: Convert ovs-vlan-test to rST")
Acked-by: Ben Pfaff <blp@ovn.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

build-aux/dist-docs

@@ -43,7 +43,7 @@ rm -rf $distdir
 mkdir $distdir
 
 # Install manpages.
-${MAKE-make} install-man mandir="$abs_distdir"/man
+${MAKE-make} install-man install-man-rst mandir="$abs_distdir"/man
 (cd $distdir && mv `find man -type f` . && rm -rf man)
 manpages=`cd $distdir && echo *`