Add readability-redundant-* checks

There's a number of redundancies in our code that clang can sanitize
out.  Fix the existing problems, and enable the checks.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ie63d7b7f0777b702fbf1b23a24e1bed7b4f5183b
diff --git a/include/authorization.hpp b/include/authorization.hpp
index 27d7b32..f8e74b9 100644
--- a/include/authorization.hpp
+++ b/include/authorization.hpp
@@ -85,7 +85,7 @@
     // needed.
     // This whole flow needs to be revisited anyway, as we can't be
     // calling directly into pam for every request
-    std::string unsupportedClientId = "";
+    std::string unsupportedClientId;
     return persistent_data::SessionStore::getInstance().generateUserSession(
         user, clientIp, unsupportedClientId,
         persistent_data::PersistenceType::SINGLE_REQUEST, isConfigureSelfOnly);