lsa: make base class abstract

refs: #4353

Change-Id: If95c1689727f541c123623d21aec78ab8bdd58e6
diff --git a/src/lsa.cpp b/src/lsa.cpp
index 1b5e804..9c05710 100644
--- a/src/lsa.cpp
+++ b/src/lsa.cpp
@@ -59,7 +59,7 @@
 }
 
 std::string
-NameLsa::getData()
+NameLsa::getData() const
 {
   std::ostringstream os;
   os << m_origRouter << "|" << Lsa::Type::NAME << "|" << m_lsSeqNo << "|"
@@ -165,7 +165,7 @@
 }
 
 std::string
-CoordinateLsa::getData()
+CoordinateLsa::getData() const
 {
   std::ostringstream os;
   os << m_origRouter << "|" << Lsa::Type::COORDINATE << "|" << m_lsSeqNo << "|"
@@ -258,7 +258,7 @@
 }
 
 std::string
-AdjLsa::getData()
+AdjLsa::getData() const
 {
   std::ostringstream os;
   os << m_origRouter << "|" << Lsa::Type::ADJACENCY << "|" << m_lsSeqNo << "|"
@@ -402,6 +402,8 @@
     return "COORDINATE";
   case nlsr::Lsa::Type::NAME:
     return "NAME";
+  case nlsr::Lsa::Type::MOCK:
+    return "MOCK";
   default:
     return "BASE";
   }