Small cleanup of GlobalToolCommandlet from PR #684

[hohwille]

From PR #684 we have some small left-overs from the review discussion:

• [ ] Move postInstall() to LocalToolCommandlet and remove it from [Global]ToolCommandlet:

  But what are we doing with postInstall() https://github.com/devonfw/IDEasy/blob/071e732e6c74aed7b12ccc1d522faf1c4a015dad/cli/src/main/java/com/devonfw/tools/ide/tool/GlobalToolCommandlet.java#L142-L144

• [x] Improve log statement of GlobalToolCommandlet: https://github.com/devonfw/IDEasy/blob/55db46d0e936fd7e81aaa353b786bc8b825a04e8/cli/src/main/java/com/devonfw/tools/ide/tool/GlobalToolCommandlet.java#L149

  If the process runs in background mode, then message Successfully installed docker in version 1.16.0 will be output immediately after the setup installer window has opened.

  We can change the log message but this is the only reasonable behaviour. We trigger the installation and the end-user needs to click through the installation process. This can take a minute or several hours if the user has fallen asleep. Not much that we can do about it...