fix: make keepalive params a bit conservative (googleapis#528)

Author: sushanb

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/BigtableDataSettings.java

@@ -124,10 +124,9 @@ public ManagedChannelBuilder apply(ManagedChannelBuilder input) {
                         return input.usePlaintext();
                       }
                     })
-                .setKeepAliveTime(Duration.ofSeconds(10)) // sends ping in this interval
+                .setKeepAliveTime(Duration.ofSeconds(30)) // sends ping in this interval
                 .setKeepAliveTimeout(
                     Duration.ofSeconds(10)) // wait this long before considering the connection dead
-                .setKeepAliveWithoutCalls(true) // sends ping without active streams
                 .build());
 
     LOGGER.info("Connecting to the Bigtable emulator at " + hostname + ":" + port);

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubSettings.java

@@ -245,10 +245,9 @@ public static InstantiatingGrpcChannelProvider.Builder defaultGrpcTransportProvi
     return BigtableStubSettings.defaultGrpcTransportProviderBuilder()
         .setPoolSize(getDefaultChannelPoolSize())
         .setMaxInboundMessageSize(MAX_MESSAGE_SIZE)
-        .setKeepAliveTime(Duration.ofSeconds(10)) // sends ping in this interval
+        .setKeepAliveTime(Duration.ofSeconds(30)) // sends ping in this interval
         .setKeepAliveTimeout(
             Duration.ofSeconds(10)) // wait this long before considering the connection dead
-        .setKeepAliveWithoutCalls(true) // sends ping without active streams
         // TODO(weiranf): Set this to true by default once DirectPath goes to public beta
         .setAttemptDirectPath(isDirectPathEnabled());
   }