Restore modified tags after TZ manipulation

This ensures that Xmp date/times that have been set by the user aren't
over written by the TZ restoration efforts. This fixes bug #1998

src/xmpsidecar.cpp

@@ -144,11 +144,6 @@ namespace Exiv2 {
             copyExifToXmp(exifData_, xmpData_);
             copyIptcToXmp(iptcData_, xmpData_);
 
-            // #589 - restore tags which were modified by the convertors
-            for (auto&& it : copy) {
-                xmpData_[it.key()] = it.value();
-            }
-
             // #1112 - restore dates if they lost their TZ info
             for (auto&& date : dates_) {
                 std::string sKey = date.first;
@@ -163,6 +158,11 @@ namespace Exiv2 {
                 }
             }
 
+            // #589 - restore tags which were modified by the convertors
+            for (auto&& it : copy) {
+                xmpData_[it.key()] = it.value();
+            }
+
             if (XmpParser::encode(xmpPacket_, xmpData_,
                                   XmpParser::omitPacketWrapper|XmpParser::useCompactFormat) > 1) {
 #ifndef SUPPRESS_WARNINGS