fix bug in install-flink.py
fix bug in install-flink.py

wangyangjun/RealtimeStreamBenchmark,wangyangjun/StreamBench,wangyangjun/RealtimeStreamBenchmark,wangyangjun/StreamBench,wangyangjun/RealtimeStreamBenchmark,wangyangjun/StreamBench,wangyangjun/RealtimeStreamBenchmark,wangyangjun/StreamBench,wangyangjun/RealtimeStreamBenchmark,wangyangjun/RealtimeStreamBenchmark,wangyangjun/RealtimeStreamBenchmark,wangyangjun/StreamBench,wangyangjun/StreamBench,wangyangjun/StreamBench,wangyangjun/RealtimeStreamBenchmark,wangyangjun/StreamBench,wangyangjun/RealtimeStreamBenchmark,wangyangjun/StreamBench