Default interface isn't working

[spficklin]

Currently Granny gives the error if no arguments are provided

Error: unknown interface

By default it is supposed to use 'cli' as the default interface if none is provided

[nhanng24]

For consistency, I think we should make the program ask the user to provide an argument for the interface, rather than having the default interface argument. I will overrides the argparser to print out the help menu for the user to choose from the list of argument rather than automatically assign a default value.