helios-use: print a message before fetching available versions
helios-use: print a message before fetching available versions

Sometimes curling index.docker.io can take a few seconds or more, so add
a brief notice message prior to firing off the request to reduce any
confusion about why `helios-use` is paused for several seconds.

mattnworb/helios,mattnworb/helios,spotify/helios,spotify/helios,mavenraven/helios,mattnworb/helios,mavenraven/helios,mavenraven/helios,spotify/helios