Connection Strategy MOCK_* isn't honored when using ServerPool

[andrewjroth]

Hello,

It seems that Mocking methodology described in Mocking doesn't work correctly when using a ServerPool instead of a single Server. This limits the usefulness of the Mocking if the connection setup must be completely changed.

Test Case

import ldap3
server = ldap3.Server('my_fake_server')
server_pool = ldap3.ServerPool(
    [server],
    ldap3.FIRST,
    active=1,  # Loop through all servers once.
    exhaust=10,  # Remove unreachable servers for 10 seconds.
)
connection = ldap3.Connection(server_pool,
                              user='cn=my_user,ou=test,o=lab',
                              password='my_password',
                              client_strategy=ldap3.MOCK_SYNC)
connection.bind()

print("Test Complete")

Expected Result

Code to run without error using a mocked connection and print Test Complete at the end.

Actual Result

Traceback (most recent call last):
  File "ldap3_mock_test.py", line 13, in <module>
    connection.bind()
  File "/home/andrew/IdeaProjects/flask-ldap3-login/venv/lib/python3.8/site-packages/ldap3/core/connection.py", line 589, in bind
    self.open(read_server_info=False)
  File "/home/andrew/IdeaProjects/flask-ldap3-login/venv/lib/python3.8/site-packages/ldap3/strategy/sync.py", line 57, in open
    BaseStrategy.open(self, reset_usage, read_server_info)
  File "/home/andrew/IdeaProjects/flask-ldap3-login/venv/lib/python3.8/site-packages/ldap3/strategy/base.py", line 122, in open
    new_server = self.connection.server_pool.get_server(self.connection)  # get a server from the server_pool if available
  File "/home/andrew/IdeaProjects/flask-ldap3-login/venv/lib/python3.8/site-packages/ldap3/core/pooling.py", line 317, in get_server
    return self.pool_states[connection].get_server()
  File "/home/andrew/IdeaProjects/flask-ldap3-login/venv/lib/python3.8/site-packages/ldap3/core/pooling.py", line 84, in get_server
    self.last_used_server = self.find_active_server(starting=0)
  File "/home/andrew/IdeaProjects/flask-ldap3-login/venv/lib/python3.8/site-packages/ldap3/core/pooling.py", line 187, in find_active_server
    raise LDAPServerPoolExhaustedError('no active server available in server pool after maximum number of tries')
ldap3.core.exceptions.LDAPServerPoolExhaustedError: no active server available in server pool after maximum number of tries