Move global flags to rootCmd

Flags like `--addr` or `--system-admin-key` are attached to each individual command and not to rootCmd, which makes a bit painful to use.

e.g.
./ionscale_linux_amd64   --addr https://ion.xxx.com  machine --help
retuns
`Error: unknown flag: --addr`

which then requires removing the flags again to check the help.