Unstable work keystone+TLS via LDAP proxy

When there is a configuration: keystone+TLS (with domains are enabled) via LDAP proxy we get unstable keystone work.
It's reflected in the fact that i.e. keystone returns user list of some ldap domain or it is failed:

root@node-3:/etc/ldap# OS_IDENTITY_API_VERSION=3 openstack user list --domain mirantis.tld
An unexpected error prevented the server from fulfilling your request. (HTTP 500) (Request-ID: req-0b41a6d8-6f83-43d4-bfed-99704817e0ec)

-----

root@node-3:/etc/ldap# OS_IDENTITY_API_VERSION=3 openstack user list --domain mirantis.tld
+------------------------------------------------------------------+-------+
| ID | Name |
+------------------------------------------------------------------+-------+
| 5e3712f0a4f1e05d6e0c4f8909340424dc21ad70de354b39cdf22a68c45b978f | demo |
| bbe729e29e55faf9f68a79d9d98f52b1a7fd35277b4abc1a54065cfceb0b8084 | demo2 |
| 511b2c2670a05e869d1275f417e75ec9525992a1fe677a9acc574e3b86818e64 | demo3 |
+------------------------------------------------------------------+-------+

In keystone logs we have such errors:

---------
REQ: curl -g -i -X GET http://192.168.0.2:35357/v3/users?domain_id=4416beef97cb4735939be0eae5faea56 -H "User-Agent: python-keystoneclient" -H "Accept: application/json" -H "X-Auth-Token: {SHA1}ee5362256c46ef7262830720c82f8840f83bd6fa"
Resetting dropped connection: 192.168.0.2
"GET /v3/users?domain_id=4416beef97cb4735939be0eae5faea56 HTTP/1.1" 500 143
RESP: [500] Content-Length: 143 Vary: X-Auth-Token Server: Apache Connection: close Date: Wed, 22 Jun 2016 18:43:34 GMT Content-Type: application/json x-openstack-request-id: req-75bf37fb-32c4-4db4-87e5-1ec084fb788f
RESP BODY: {"error": {"message": "An unexpected error prevented the server from fulfilling your request.", "code": 500, "title": "Internal Server Error"}}
---------

<12>Jun 23 11:00:27 node-3 keystone-admin: 2016-06-23 11:00:27.873 22793 WARNING keystone.common.manager [req-e58f97a1-79f8-4186-8cb1-ec09f5bfc5c8 - - - - -] Deprecated: Direct import of driver 'keystone.identity.backends.ldap.Identity' is deprecated as of Liberty in favor of its entrypoint from 'keystone.identity' and may be removed in N.
<15>Jun 23 11:00:27 node-3 keystone-admin: 2016-06-23 11:00:27.878 22793 DEBUG keystone.common.manager [req-e58f97a1-79f8-4186-8cb1-ec09f5bfc5c8 - - - - -] Failed to load 'keystone.identity.backends.ldap.Identity' using stevedore: No 'keystone.identity' driver found, looking for 'keystone.identity.backends.ldap.Identity' load_driver /usr/lib/python2.7/dist-packages/keystone/common/manager.py:77
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