message: post review fix, simplifying flow in do_try_begin_write()
diff: @@ -1847,13 +1847,10 @@ bool SharedGroup::do_try_begin_write()
  // the write mutex. For this case we are trivially fair and can ignore the
  // fairness machinery.
  bool got_the_lock = m_writemutex.try_lock();
  - if (!got_the_lock) {
  - return false;
  - }
  - else {
  + if (got_the_lock) {
  finish_begin_write();
  - return true;
  }
  + return got_the_lock;
  }
  