(GH-531) Fix - Powershell v2 fails to download SSL v3 files

Powershell, which uses the .NET Framework v2, has a bug that prevents it from
falling back to SSL3 when TLS doesn't properly download files. So it causes the
response to timeout because it never receives a response.

This forces the security protocol to SSL3 when using Poshv2.
(GH-531) PowerShell v2 Fallback to SSL v3 if request failure

Limit the fallback to only when there is a failure in the webrequest. This way
TLS downloads could still work.
v0.9.8.28-alpha1
Merge branch 'stable'

* stable:
  v0.9.8.28-alpha1
  (GH-531) PowerShell v2 Fallback to SSL v3 if request failure
  (GH-531) Fix - Powershell v2 fails to download SSL v3 files