CB-13889 Allow test failures for Visual Studio 2017 environments (#263)

diff --git a/appveyor.yml b/appveyor.yml
index 19e7f28..3eb6194 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -37,6 +37,10 @@
     - nodejs_version: "4"
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
 
+matrix:
+  allow_failures:
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+
 install:
   - ps: Install-Product node $env:nodejs_version
   - npm install