--disable-password is not supported on Amazon Linux

[jrstarke]

When calling adduser on Amazon Linux, it aliases to useradd, which does not have the --disable-password or --gecos flags.

[kislyuk]

Thanks for reporting, could you provide an equivalent command that should be run on that system?

[e7hz3r0]

For --disabled-password, it appears that passwords are disabled by default on Amazon Linux so there's no equivalent flag (none necessary).

For --gecos, the equivalent is --comment

[lindenle]

I attempted to create a fix #16