goal: Better handling of obsoleted pkg installation

In situation where a package exists in multiple versions and some older
version is being obsoleted, any of obsoleters was considered a valid
solution.

The result could be really misleading. For example let's have this package set:

systemd-udev-1.0

systemd-udev-2.0
Obsoletes: systemd-udev < 2

systemd-boot-unsigned-2.0
Obsoletes: systemd-udev < 2

In this case `dnf install systemd-udev` may lead to installation of
systemd-boot-unsigned which is probably not what the user expected. The
reason is the split in the upgrade-path created by obsolete and both
branches - systemd-udev-2.0 and systemd-boot-unsigned-2.0 are considered
valid.

With this patch install command takes into account only obsoleters of
the best version of the package so the `dnf install systemd-udev`
results in correct installation of systemd-udev-2.0 package.

libdnf/base/goal.cpp

@@ -45,8 +45,25 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 namespace {
 
 void add_obsoletes_to_data(const libdnf::rpm::PackageQuery & base_query, libdnf::rpm::PackageSet & data) {
+    libdnf::rpm::PackageQuery data_query(data);
+
+    // In case there is an installed package in the `data` behave consistently
+    // with upgrade and add all the obsoleters.
+    libdnf::rpm::PackageQuery installed_data(data_query);
+    installed_data.filter_installed();
+
+    if (installed_data.empty()) {
+        // If there is no installed package in the `data`, add only obsoleters
+        // of the latest versions.  This should prevent unexpected results in
+        // case a package has multiple versions and some older version is being
+        // obsoleted.
+        // See also https://bugzilla.redhat.com/show_bug.cgi?id=2176263
+        data_query.filter_priority();
+        data_query.filter_latest_evr();
+    }
+
     libdnf::rpm::PackageQuery obsoletes_query(base_query);
-    obsoletes_query.filter_obsoletes(data);
+    obsoletes_query.filter_obsoletes(data_query);
     data |= obsoletes_query;
 }