Add check for usernames in Shell()
Add check for usernames in Shell()

If given username is not defined, then
it tries ['root', 'ubuntu', 'ec2-user', 'amazon']

zBMNForks/mist.io,DimensionDataCBUSydney/mist.io,DimensionDataCBUSydney/mist.io,johnnyWalnut/mist.io,Lao-liu/mist.io,DimensionDataCBUSydney/mist.io,munkiat/mist.io,kelonye/mist.io,Lao-liu/mist.io,munkiat/mist.io,munkiat/mist.io,DimensionDataCBUSydney/mist.io,johnnyWalnut/mist.io,afivos/mist.io,johnnyWalnut/mist.io,kelonye/mist.io,zBMNForks/mist.io,munkiat/mist.io,afivos/mist.io,kelonye/mist.io,Lao-liu/mist.io,afivos/mist.io,Lao-liu/mist.io,zBMNForks/mist.io