qa-tests: fix the cause of rpc tests failing intermittently (#13871)

In this PR we try to save and then restore the previous chaindata.

.github/workflows/qa-tip-tracking.yml

@@ -36,9 +36,10 @@ jobs:
       run: |
         python3 $ERIGON_QA_PATH/test_system/db-producer/pause_production.py || true
 
-    - name: Clean Erigon Chaindata Directory
+    - name: Save Erigon Chaindata Directory
+      id: save_chaindata_step
       run: |
-        rm -rf $ERIGON_REFERENCE_DATA_DIR/chaindata
+        mv $ERIGON_REFERENCE_DATA_DIR/chaindata $ERIGON_TESTBED_AREA/chaindata-prev
 
     - name: Run Erigon, wait sync and check ability to maintain sync
       id: test_step
@@ -115,10 +116,11 @@ jobs:
         name: metric-plots
         path: ${{ github.workspace }}/metrics-${{ env.CHAIN }}-plots*
 
-    - name: Clean Erigon Chaindata Directory
-      if: always()
+    - name: Restore Erigon Chaindata Directory
+      if: steps.save_chaindata_step.outcome == 'success'
       run: |
         rm -rf $ERIGON_REFERENCE_DATA_DIR/chaindata
+        mv $ERIGON_TESTBED_AREA/chaindata-prev $ERIGON_REFERENCE_DATA_DIR/chaindata
 
     - name: Resume the Erigon instance dedicated to db maintenance
       run: |