TT#78950 improve ngcp-update-db 3308 sync

* determine the master db node name to use
      for ngcp-sync-db master-slave replication restoration
      if the CENTRAL_DBHOST is set by default to db01 only.
      if the current nodename ends with "a" then db01a is used,
      otehrwise db01b is used as the master host. that is
      to make sure that during the upgrade the correct "side"
      is used to replicate the data from and avoid lossy
      statements that break replication.

Change-Id: I1a51bd0d975390d9269ef5208ce8275f9e055a1f
(cherry picked from commit 1cfafba736)

ngcp-update-db-schema

@@ -257,6 +257,20 @@ if $RUN_SYNC_DB && ($NOT_REPLICATED_REV_APPLIED || [ -n "$AUTOMATED_INSTALL_MODE
       if [ -n "$AUTOMATED_INSTALL_MODE" ] ; then
           EXTRA_SYNC_DB_OPTS="--local-user=root --set-local-grants"
       fi
+
+      # determine the preferred db node a or b if the default db01 is the constants
+      MASTER_NODE_PREF=""
+      if [ "$CENTRAL_DBHOST" == "db01" ] ; then
+        NODE_SIDE="a"
+        if [[ "$nodename" == *b ]] ; then
+          NODE_SIDE="b"
+        fi
+        MASTER_NODE_PREF="db01${NODE_SIDE}"
+      fi
+      if [ -n "$MASTER_NODE_PREF" ] ; then
+        EXTRA_SYNC_DB_OPTS="$EXTRA_SYNC_DB_OPTS --master-host $MASTER_NODE_PREF"
+      fi
+
       # shellcheck disable=SC2086
       if /usr/sbin/ngcp-sync-db --verbose --force --use-central-db --repl-mode "master-slave" --databases "${PRX_SYNC_DBS}" --ignore-tables "${PRX_IGNORE_TABLES}" --ssh-tunnel=33125 ${EXTRA_SYNC_DB_OPTS} --local-host=${LOCAL_DBHOST} --local-port=${LOCAL_DBPORT}; then
           echo "Syncing 'not_replicated' statements from the central node."