tests: Add complex test with valgrind

There was only simple write and read test under valgrind. This commit
introduces a test which checks more use cases:
* mkdir
* create file
* rename file
* ls -l on dir
* truncate up&down file
* set trash time
* make snapshot
* CopyOnWrite
* concurrent writes and reads
* remove file
* unlink file
* restart master server
* restart chunkserver