[master] changed the return value of findNSECCover() from RRsetPtr to ConstRRsetptr.

This will fix build failure due to the mixture of these in ?:.  (and in any
event when we can make something const that's generally good to do)

src/lib/datasrc/database.cc

@@ -352,7 +352,7 @@ FINAL_TYPES() {
 
 }
 
-RRsetPtr
+ConstRRsetPtr
 DatabaseClient::Finder::findNSECCover(const Name& name) {
     try {
         // Which one should contain the NSEC record?
@@ -387,7 +387,7 @@ DatabaseClient::Finder::findNSECCover(const Name& name) {
             arg(accessor_->getDBName()).arg(name);
     }
     // We didn't find it, return nothing
-    return (RRsetPtr());
+    return (ConstRRsetPtr());
 }
 
 DatabaseClient::Finder::DelegationSearchResult

src/lib/datasrc/database.h

@@ -1037,7 +1037,7 @@ public:
         /// This one calls findPreviousName on the given name and extracts an
         /// NSEC record on the result. It handles various error cases. The
         /// method exists to share code present at more than one location.
-        dns::RRsetPtr findNSECCover(const dns::Name& name);
+        dns::ConstRRsetPtr findNSECCover(const dns::Name& name);
 
         /// \brief Convenience type shortcut.
         ///