#2567 log: duplicated code in lga_client and lga_stream

[Vu Minh Nguyen]

LogClient and LogStreamInfo class have same three methods with same code, they are:

```c++
int32_t FetchAndIncreaseRefCounter(bool* updated);
int32_t FetchAndDecreaseRefCounter(bool* updated);
void RestoreRefCounter(RefCounterDegree value, bool updated);
```

It is better to create independent RefCounter class with these methods.

[Vu Minh Nguyen]

commit ffbeba61513e28ce862eaa735ed75e8243f881b8 (HEAD, origin/develop, develop)
Author: Vu Minh Nguyen vu.m.nguyen@dektech.com.au
Date: Mon Oct 2 09:34:50 2017 +0700

log: remove duplicated code in lga_client and lga_stream [#2567]

Introduce `RefCounter` class to remove duplicated code in LogClient
and LogStreamInfo. Introduce also one new parameter `caller`,
the purpose mainly is for debugging.