Log路径生成失败

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设备：nexus 6
版本：Android 7.1.1
blockcanary版本：1.5.0

堆栈信息如下：
ava.io.FileNotFoundException: /data/storage/emulated/0/Android/data/com.test.testapm/cache/looper-2018-07-06_17-09-29.376.log (No such file or directory)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.(FileOutputStream.java:221)
at java.io.FileOutputStream.(FileOutputStream.java:140)
at com.github.moduth.blockcanary.LogWriter.save(LogWriter.java:108)
at com.github.moduth.blockcanary.LogWriter.save(LogWriter.java:56)
at com.github.moduth.blockcanary.BlockCanaryInternals$1.onBlockEvent(BlockCanaryInternals.java:63)
at com.github.moduth.blockcanary.LooperMonitor$1.run(LooperMonitor.java:80)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.os.HandlerThread.run(HandlerThread.java:61)

发现BlockCanaryInternals#getPath方法中，最后在目录前面加上了Data目录，导致目录生成失败。

Start with BlockCanaryInternals#getPath and compare the generated directory with the path used by LogWriter.save at LogWriter.java:108. Reproduce the failure on the reported Android configuration if available, then verify that log creation no longer raises FileNotFoundException and that the generated path is valid.

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