[rrd4j] Improve logging of exceptions thrown by getDB (openhab#14068)

Add exception message for better identification of root cause.

Signed-off-by: Holger Friedrich <[email protected]>

bundles/org.openhab.persistence.rrd4j/src/main/java/org/openhab/persistence/rrd4j/internal/RRD4jPersistenceService.java

@@ -156,7 +156,7 @@ public synchronized void store(final Item item, @Nullable final String alias) {
         try {
             db = getDB(name);
         } catch (Exception e) {
-            logger.warn("Failed to open rrd4j database '{}' ({})", name, e.getClass().getName());
+            logger.warn("Failed to open rrd4j database '{}' to store data ({})", name, e.toString());
         }
         if (db == null) {
             return;
@@ -258,7 +258,7 @@ public Iterable<HistoricItem> query(FilterCriteria filter) {
         try {
             db = getDB(itemName);
         } catch (Exception e) {
-            logger.warn("Failed to open rrd4j database '{}' ({})", itemName, e.getClass().getName());
+            logger.warn("Failed to open rrd4j database '{}' for querying ({})", itemName, e.toString());
             return List.of();
         }
         if (db == null) {