Fixes setup compatibility issue on Windows

Fixes Bug #1052161

"python setup.py build" fails on Windows due to a hardcoded shell path:
/bin/sh

Change-Id: I9b5838aa96d3f41f8baf58f28d3e9e6d9646f6cb

keystoneclient/openstack/common/setup.py

@@ -116,8 +116,12 @@ def write_requirements():
 
 
 def _run_shell_command(cmd):
-    output = subprocess.Popen(["/bin/sh", "-c", cmd],
-                              stdout=subprocess.PIPE)
+    if os.name == 'nt':
+        output = subprocess.Popen(["cmd.exe", "/C", cmd],
+                                  stdout=subprocess.PIPE)
+    else:
+        output = subprocess.Popen(["/bin/sh", "-c", cmd],
+                                  stdout=subprocess.PIPE)
     out = output.communicate()
     if len(out) == 0:
         return None