[2386] Fix NSEC parser to work during whole zone loading

src/lib/dns/rdata/generic/detail/nsec_bitmap.cc

@@ -132,7 +132,7 @@ buildBitmapsFromLexer(const char* const rrtype_name,
     bool have_rrtypes = false;
     while (true) {
         const MasterToken& token = lexer.getNextToken();
-        if (token.getType() == MasterToken::END_OF_FILE) {
+        if (token.getType() != MasterToken::STRING) {
             break;
         }
 
@@ -148,6 +148,8 @@ buildBitmapsFromLexer(const char* const rrtype_name,
         }
     }
 
+    lexer.ungetToken();
+
     if (!have_rrtypes) {
          isc_throw(InvalidRdataText,
                    rrtype_name << " record does not end with RR type mnemonic");