1. use MySQL headers instead of system ones;
  2. move logical part of code into a separate function.


server-tools/instance-manager/angel.cc:
  Polishing: try not to use system headers.
  Use headers from include/ directory when it is possible.
server-tools/instance-manager/manager.cc:
  Polishing: move logical part of code into a separate function.
server-tools/instance-manager/manager.h:
  Polishing: move logical part of code into a separate function.
server-tools/instance-manager/mysqlmanager.cc:
  Polishing: rollback rename.