bug 4131 have subscription so edit routing if one exists

bug 4131 have subscription so edit routing if one exists

Changes the template variable checked in serials-menu.inc for determining where to
show 'Create Routing List' or 'Edit Routing List' to hasRouting.

Also adds the $hasRouting variable to serials/routing.pl and serials/routing-preview.pl,
for completeness.

Signed-off-by: Ian Walls <ian.walls@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
(cherry picked from commit b7fdfc1384a749471f2c9a00b910b063778085e2)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>