reduce error logging when fee and exchanges rate sources are unavailable

src/main/java/com/sparrowwallet/sparrow/net/ExchangeSource.java

@@ -56,7 +56,11 @@ public enum ExchangeSource {
                 Gson gson = new Gson();
                 return gson.fromJson(reader, CoinbaseRates.class);
             } catch (Exception e) {
-                log.error("Error retrieving currency rates", e);
+                if(log.isDebugEnabled()) {
+                    log.warn("Error retrieving currency rates", e);
+                } else {
+                    log.warn("Error retrieving currency rates (" + e.getMessage() + ")");
+                }
                 return new CoinbaseRates();
             }
         }
@@ -87,7 +91,11 @@ public enum ExchangeSource {
                 Gson gson = new Gson();
                 return gson.fromJson(reader, CoinGeckoRates.class);
             } catch(Exception e) {
-                log.error("Error retrieving currency rates", e);
+                if(log.isDebugEnabled()) {
+                    log.warn("Error retrieving currency rates", e);
+                } else {
+                    log.warn("Error retrieving currency rates (" + e.getMessage() + ")");
+                }
                 return new CoinGeckoRates();
             }
         }

src/main/java/com/sparrowwallet/sparrow/net/FeeRatesSource.java

@@ -87,7 +87,11 @@ public enum FeeRatesSource {
                 blockTargetFeeRates.put(Integer.MAX_VALUE, threeTierRates.minimumFee);
             }
         } catch (Exception e) {
+            if(log.isDebugEnabled()) {
                 log.warn("Error retrieving recommended fee rates from " + url, e);
+            } else {
+                log.warn("Error retrieving recommended fee rates from " + url + " (" + e.getMessage() + ")");
+            }
         }
 
         return blockTargetFeeRates;