bug 1373068 - fix the ctypes declaration of SSL_ClearSessionCache in head_psm.js r=Cykesiopka

SSL_ClearSessionCache is `void SSL_ClearSessionCache()`. In head_psm.js it was
being declared as `SECStatus SSL_ClearSessionCache()` and the "return value" was
being checked, which was incorrect. This apparently wasn't causing failures on
any of our test runs, but with tsan enabled the check would fail.

MozReview-Commit-ID: 6KosOVPu8K4

--HG--
extra : rebase_source : 73addb80a5ab5263a182207a0f4277daf8ae32a5

security/manager/ssl/tests/unit/head_psm.js

@@ -238,15 +238,18 @@ function clearSessionCache() {
   let SSL_ClearSessionCache = null;
   try {
     SSL_ClearSessionCache =
-      _getLibraryFunctionWithNoArguments("SSL_ClearSessionCache", "ssl3");
+      _getLibraryFunctionWithNoArguments("SSL_ClearSessionCache", "ssl3",
+                                         ctypes.void_t);
   } catch (e) {
     // On Windows, this is actually in the nss3 library.
     SSL_ClearSessionCache =
-      _getLibraryFunctionWithNoArguments("SSL_ClearSessionCache", "nss3");
+      _getLibraryFunctionWithNoArguments("SSL_ClearSessionCache", "nss3",
+                                         ctypes.void_t);
   }
-  if (!SSL_ClearSessionCache || SSL_ClearSessionCache() != 0) {
-    throw new Error("Failed to clear SSL session cache");
+  if (!SSL_ClearSessionCache) {
+    throw new Error("couldn't get SSL_ClearSessionCache");
   }
+  SSL_ClearSessionCache();
 }
 
 function getSSLStatistics() {