Reduce unnecessary includes in common.hpp

Also, make Decryptor::doDecrypt() static

Refs: #4755
Change-Id: I21b05897e31fc98697b60b7305ac865962e699c4
diff --git a/src/access-manager.cpp b/src/access-manager.cpp
index 0093d57..70ad8be 100644
--- a/src/access-manager.cpp
+++ b/src/access-manager.cpp
@@ -22,6 +22,7 @@
 
 #include <ndn-cxx/security/signing-helpers.hpp>
 #include <ndn-cxx/util/logger.hpp>
+#include <ndn-cxx/util/random.hpp>
 
 namespace ndn::nac {