Fix displaying usage for make_cert.sh

Now, if no arguments are passed to make_cert.sh script, it will fail on:

  tools/make_cert.sh: line 30: [: missing `]'

and might go on with generating certs depending on the bash settings.
It is fixed within this patch.

Change-Id: I62bf9c972ebd1644da622439e05114f245f20809
1 file changed