Juju machine service for Windows creates incorrect tools symlinks

[Adrian Vladu]

On Windows 2012 R2, jujud service creates incorrect symlinks for charm units tools.
All the created symlinks for charm units point to the jujud file of the the first deployed charm.

Steps to reproduce the bug:
  1. Deploy on one Windows 2012 R2 machine one unit of two different charms: charm-one and charm-two.
  2. Destroy charm-one.

Effects:
   The tools directory of charm-one will be deleted, when the charm unit is destroyed.
   Every juju command for the charm-two, such as relation-get.exe, will point to a nonexistent file.
   For example:
       C:\juju\lib\agents\tools\unit-charm-two-0\config-get.exe -> C:\juju\lib\agents\tools\unit-charm-one-0\config-get.exe
   Moreover:
      C:\juju\lib\agents\tools\jujud-machine<nr>\config-get.exe -> C:\juju\lib\agents\tools\unit-charm-one-0\config-get.exe
  This will cause each command execution to fail.

Tested on Juju version 1.22.

Cause:
  The following Go code that handles the symlinks' creation does not support Windows:
   https://github.com/juju/juju/blob/master/worker/uniter/runner/jujuc/tools.go#L31

[Gabriel Samfira (gabriel-samfira)]

This bug is addressed by:

http://reviews.vapour.ws/r/1643/
http://reviews.vapour.ws/r/1644/