java_sdk_library: Stop disabling copy to dist when sdk_version: none

Previously, setting "sdk_version: none" would have a side effect of
disabling copying to dist by default. This change removes that behavior
and will copy to dist by default unless explicitly specified.

This will have no impact on the dist because all java_sdk_library
modules that relied on the previous behavior to disable copying to
dist have been modified to explicitly disable copying to dist.

Test: lunch sdk-eng && m dist sdk
      compare out/dist/apistubs directories before and after this
      change to make sure that they have not changed.
Bug: 173715943
Change-Id: I376546b5a8b03de6c944961f7408dad22184fe49