package/mender: add missing double quote in service file

There was a missing double quotes that would prevent the service from
starting.

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
Tested-by: Angelo Compagnucci <angelo@amarulasolutions.com>
Acked-by: Angelo Compagnucci <angelo@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/mender/mender.service

@@ -12,7 +12,7 @@ if [ -L /var/lib/mender \
     if rm -f /var/lib/mender >/dev/null 2>&1; then \
         mkdir -p /var/lib/mender; \
     else \
-        echo "No persistent location to store mender data. Data will be lost\
+        echo "No persistent location to store mender data. Data will be lost" \
         echo "at reboot. Are you sure this is what you want to do?"; \
         mkdir -p "$(readlink /var/lib/mender)"; \
     fi; \