Disambiguity of all the implemented locks

[thsfs]

Found a warning when building the node for Windows.

...
warning C4930: 'std::unique_lock<nano::mutex> lock(nano::mutex)': prototyped function not called (was a variable definition intended?)
...

This is related to an ambiguity described by the wiki, where the C++ compiler tries to declare a function as lock instead of creating an object for it.

The best approach is to use the uniform initialization {} when there is any argument. The warning was issued only for vote_processor.cpp, but decided to change all the mutex lock object creations.

[dsiganos]

I find it annoying that our formatter treat {} differently from ().
It remove a space before { and adds spaces inside the brackets.

-                       nano::lock_guard<nano::mutex> lk (connections_mutex);
+                       nano::lock_guard<nano::mutex> lk{ connections_mutex };

[thsfs]

I find it annoying that our formatter treat {} differently from (). It remove a space before { and adds spaces inside the brackets.

-                       nano::lock_guard<nano::mutex> lk (connections_mutex);
+                       nano::lock_guard<nano::mutex> lk{ connections_mutex };

Yes, but in another perspective it is easier to spot the difference.