[no-relnote] Fix Dockerfile lint issues

[elezar]

This removes the following warnings when building the docker containers:

 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 65)
 - UndefinedVar: Usage of undefined variable '$VERSION' (line 81)
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 18)
 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 39)
 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 40)