- BUG#22306: STOP INSTANCE can not be applied for instances in Crashed,
    Failed and Abandoned;
  - BUG#23476: DROP INSTANCE does not work
  - BUG#23215: STOP INSTANCE takes too much time

BUG#22306:
The problem was that STOP INSTANCE checked that mysqld is up and running.
If it was not so, STOP INSTANCE reported an error. Now, STOP INSTANCE
reports an error if the instance has been started (mysqld can be down).

BUG#23476:
The problem was that DROP INSTANCE tried to stop inactive instance. The fix is
trivial.

BUG#23215:
The problem was that locks were not acquired properly, so the
instance-monitoring thread could not acquire the mutex, holded by the
query-processing thread.

The fix is to simplify locking scheme by moving instance-related information to
Instance-class out of Guardian-class. This allows to get rid of storing a
separate list of Instance-information in Guardian and keeping it synchronized
with the original list in Instance_map.


server-tools/instance-manager/commands.cc:
  1. Introduce Instance_cmd class -- base class for the commands
     that deal with the one instance;
  2. Remove Instance_map argument from command constructors;
  3. Ensure, that Instance Map and Instance are locked in the proper order;
  4. Polishing.
server-tools/instance-manager/commands.h:
  1. Introduce Instance_cmd class -- base class for the commands
     that deal with the one instance;
  2. Remove Instance_map argument from command constructors;
  3. Polishing.
server-tools/instance-manager/guardian.cc:
  1. Move "extended" instance information to the Instance-class.
     That allows to get rid of storing instance-related container and data in
     Guardian class, that significantly simplifies locking schema.
  2. Polishing.
server-tools/instance-manager/guardian.h:
  1. Move "extended" instance information to the Instance-class.
     That allows to get rid of storing instance-related container and data in
     Guardian class, that significantly simplifies locking schema.
  2. Polishing.
server-tools/instance-manager/instance.cc:
  1. Move "extended" instance information to the Instance-class.
  2. Introduce new state STOPPED to mark that guarded instance
     is stopped and should not be restarted by Guardian.
  3. Polishing.
server-tools/instance-manager/instance.h:
  1. Move "extended" instance information to the Instance-class.
  2. Introduce new state STOPPED to mark that guarded instance
     is stopped and should not be restarted by Guardian.
  3. Polishing.
server-tools/instance-manager/instance_map.cc:
  1. Move flush_instances() from Instance_map to Manager.
  2. Polishing.
server-tools/instance-manager/instance_map.h:
  1. Move flush_instances() from Instance_map to Manager.
  2. Polishing.
server-tools/instance-manager/instance_options.h:
  Polishing.
server-tools/instance-manager/manager.cc:
  1. Move flush_instances() from Instance_map to Manager.
  2. Polishing.
server-tools/instance-manager/manager.h:
  1. Move flush_instances() from Instance_map to Manager.
  2. Polishing.
server-tools/instance-manager/user_map.cc:
  Polishing.