move g_test_dbg_lock_sleep from a global to a function level static

This avoids the need to define that variable in every program
which uses epee.

src/blockchain_utilities/blockchain_export.cpp

@@ -31,8 +31,6 @@
 #include "common/command_line.h"
 #include "version.h"
 
-unsigned int epee::g_test_dbg_lock_sleep = 0;
-
 namespace po = boost::program_options;
 using namespace epee; // log_space