base-files: fix message of initscript wrapper

currently (after blogic's edit to my commit) it prints like this:

root@lede:/# service aa
aa does not exist. the following services are available :adblock       dnsmasq       gpio_switch   rpcd          system
boot          done          led           sqm           uhttpd
crelay        dropbear      log           sysctl        umount
cron          firewall      network       sysfixtime    urandom_seed
ddns          fstab         odhcpd        sysntpd

which looks pretty bad, and is even worse if someone writes only "service" without arguments, as it will print " does not exist. " which is confusing.

with this commit it looks like this:

root@lede:/# service
service "" not found, the following services are available:
adblock       dnsmasq       gpio_switch   rpcd          system
boot          done          led           sqm           uhttpd
crelay        dropbear      log           sysctl        umount
cron          firewall      network       sysfixtime    urandom_seed
ddns          fstab         odhcpd        sysntpd

Yes there is some play with " and ', it is to display "name" or just "" if no service name is entered (like in the example).

Signed-off-by: Alberto Bursi <alberto.bursi@outlook.it>