Corrections to widevine plugin for vts tests

Add a check for invalid session size in restoreKeys
and correct the return code when attempting to create a
plugin with an invalid uuid. Also correct the return code
when attempting to decrypt after keys have been removed.

bug:37172151
Change-Id: I7e832ffe04081471a0cdb3a9329808f47f12cfc3

libwvdrmengine/src_hidl/WVDrmFactory.cpp

@@ -44,7 +44,7 @@ Return<void> WVDrmFactory::createPlugin(
   if (!isCryptoSchemeSupported(uuid.data())) {
     ALOGE("Widevine Drm HAL: failed to create drm plugin, " \
         "invalid crypto scheme");
-    _hidl_cb(Status::BAD_VALUE, plugin);
+    _hidl_cb(Status::ERROR_DRM_CANNOT_HANDLE, plugin);
     return Void();
   }