test_filejournal.cc: cleanup memory in destructor

CID 716885 (#1 of 1): Resource leak in object (CTOR_DTOR_LEAK)
  alloc_new: Allocating memory by calling "new C_SafeCond(&this->lock,
    &this->cond, &this->done, NULL)".
  ctor_dtor_leak: The constructor allocates field "c" of "C_Sync" but
    the destructor and whatever functions it calls do not free it.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>