Allow waiting in updating records

mobile/src/main/java/be/mygod/vpnhotspot/net/monitor/TrafficRecorder.kt

@@ -64,7 +64,7 @@ object TrafficRecorder {
 
     private fun doUpdate(timestamp: Long) {
         val oldRecords = LongSparseArray<TrafficRecord>()
-        loop@ for (line in RootSession.use { it.execOutUnjoined("$IPTABLES -nvx -L vpnhotspot_fwd").drop(2) }) {
+        loop@ for (line in RootSession.use { it.execOutUnjoinedWithWait("$IPTABLES -nvx -L vpnhotspot_fwd").drop(2) }) {
             val columns = line.split("\\s+".toRegex()).filter { it.isNotEmpty() }
             try {
                 check(columns.size >= 9)

mobile/src/main/java/be/mygod/vpnhotspot/util/RootSession.kt

@@ -111,6 +111,12 @@ class RootSession : AutoCloseable {
         checkOutput(command, result, false)
         return result.out
     }
+    fun execOutUnjoinedWithWait(command: String): List<String> {
+        val result = execQuiet(command)
+        val message = checkOutput(command, result, false, false)
+        if (result.err.isNotEmpty()) Timber.i(message)
+        return result.out
+    }
     fun execOut(command: String): String = execOutUnjoined(command).joinToString("\n")
 
     /**