[FAB-6364] Make keepalive policy less restrictive

Currently the keepalive interval used for
client connections (e.g. peer to orderer)
is set to 5 min.  This setting is also
used to determine the the threshold for
how often the server will allow pings from
clients.  5 min seemed like a good default,
but in practice 1 min seems to be a better
option

Change-Id: I2f2262dfda8320d1f1731d7fd9eacf497e8cef58
Signed-off-by: Gari Singh <gari.r.singh@gmail.com>

core/comm/config.go

@@ -24,7 +24,7 @@ var (
 	maxSendMsgSize = 100 * 1024 * 1024
 	// Default keepalive options
 	keepaliveOptions = KeepaliveOptions{
-		ClientKeepaliveTime:    300,  // 5 min
+		ClientKeepaliveTime:    60,   // 1 min
 		ClientKeepaliveTimeout: 20,   // 20 sec - gRPC default
 		ServerKeepaliveTime:    7200, // 2 hours - gRPC default
 		ServerKeepaliveTimeout: 20,   // 20 sec - gRPC default