Don't hold the connection lock when calling receiveRstStream.

Closes https://github.com/square/okhttp/issues/938
Use one logger for all logging.

There was a concurrency problem in CallTest where multiple calls to
Logger.getLogger() didn't return the same instance, leading to failures
in the test.
Merge pull request #1107 from square/jwilson_1026_one_logger

Use one logger for all logging.
Merge pull request #1106 from square/jwilson_1026_fix_concurrency

Don't hold the connection lock when calling receiveRstStream.
Fix a bug where the response cache could be corrupted.

When streaming a response, we copy data from our buffer to the cached file
on disk. Unfortunately we were copying N bytes from the front of the buffer
when we wanted N bytes from the back of the buffer.

Typically these are the same, but certain access patterns can cause them
to be different, corrpting the cached file on disk.

This was uncovered by migrating the cache tests from operating on
HttpURLConnection's API to our new API.
Merge pull request #1102 from square/jwilson_1025_fix_cache_bug

Fix a bug where the response cache could be corrupted.