- change some return types from int to bool;
  - add [ERROR] tag to log_error() output;
  - add [INFO] tag to log_info() output;
  - change log messages to be more consistent.


server-tools/instance-manager/IMService.cpp:
  Log polishing.
server-tools/instance-manager/commands.cc:
  Log polishing.
server-tools/instance-manager/commands.h:
  Eliminate warnings.
server-tools/instance-manager/instance.cc:
  Log polishing.
server-tools/instance-manager/instance_map.cc:
  Log polishing.
server-tools/instance-manager/instance_options.cc:
  1) Log polishing.
  2) Change int-return type to bool.
server-tools/instance-manager/instance_options.h:
  Change int-return type to bool.
server-tools/instance-manager/listener.cc:
  Log polishing.
server-tools/instance-manager/log.cc:
  Log polishing.
server-tools/instance-manager/log.h:
  Log polishing.
server-tools/instance-manager/manager.cc:
  Log polishing.
server-tools/instance-manager/mysql_connection.cc:
  Log polishing.
server-tools/instance-manager/mysql_connection.h:
  Change int-return type to bool.
server-tools/instance-manager/mysqlmanager.cc:
  Log polishing.
server-tools/instance-manager/priv.cc:
  Log polishing.
server-tools/instance-manager/thread_registry.cc:
  1. Print pthread_t as (unsigned long), not as (signed long)
  to avoid negative identifiers in output.
  2. Print thread id after it will be initialized, not before.
server-tools/instance-manager/user_map.cc:
  Log polishing.