Can no longer save context with --user and --password

[tbeets]

I have utility scripts that create contexts for new environments including using simple username and password credentials. Using today, received error:

$ nats ctx save UserA1 --server "nats://vbox1.tinghus.net:4222" --user UserA1 --password s3cr3t                                                                 
nats: error: too many types of credentials. Choose only one from 'user/password', 'creds', 'nkey', 'token', 'nsc'

Verified no ghost context:

$ nats ctx --no-context save UserA1 --server "nats://vbox1.tinghus.net:4222" --user UserA1 --password s3cr3t
nats: error: too many types of credentials. Choose only one from 'user/password', 'creds', 'nkey', 'token', 'nsc'

Suspect this December commit broke it: 5aa2262b Jeremy Saenz 

@codegangsta @ripienaar