Restore HAS_OPENSSL.

Reviewed in https://codereview.appspot.com/7323052/.
diff --git a/oauth2client/client.py b/oauth2client/client.py
index 3370688..918539a 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -37,10 +37,13 @@
 from oauth2client import util
 from oauth2client.anyjson import simplejson
 
+HAS_OPENSSL = False
 HAS_CRYPTO = False
 try:
   from oauth2client import crypt
   HAS_CRYPTO = True
+  if crypt.OpenSSLVerifier is not None:
+    HAS_OPENSSL = True
 except ImportError:
   pass