Primary server support: introduce concept of reconnection

This patch adds two support functions for adding reconnection callbacks
and invoking such callbacks. The concept of reconnection is simple: stop
using current connection for for new queries to the server without
actually going offline.
Primary server support: basic support in failover code

Now there are two list of servers for each service. If currently
selected server is only backup, then an event will be scheduled which
tries to get connection to one of primary servers and if it succeeds,
it starts using this server instead of the one which is currently
connected to.
Primary server support: support for "disconnecting" connections in LDAP

This patch adds support for marking existing connections as being
disconnected. Each such connection can't be used for new queries and a
new one has to be created instead if necessary. This will ensure that
pending operations will end gracefully during reconnection. Also all new
queries to the server we are reconnecting to will use another (probably
newly created) connection.
Primary server support: IPA adaptation

This patch adds support for the primary server functionality into IPA
provider. No backup servers are added at the moment, just the basic
support is in place.
Primary server support: krb5 adaptation

This patch adds support for the primary server functionality
into krb5 provider. No backup servers are added at the moment,
just the basic support is in place.
Primary server support: LDAP adaptation

This patch adds support for the primary server functionality into LDAP
provider. No backup servers are added at the moment, just the basic
support is in place.
Primary server support: AD adaptation

This patch adds support for the primary server functionality into AD
provider. No backup servers are added at the moment, just the basic
support is in place.
Primary server support: man page, failover section
Primary server support: new option in ldap provider

This patch adds support for new config option ldap_backup_uri. The
description of this option's functionality is included in man page in
previous patch.
Primary server support: new options in krb5 provider

This patch adds support for new config options krb5_backup_server and
krb5_backup_kpasswd. The description of this option's functionality
is included in man page in one of previous patches.
Primary server support: new option in IPA provider

This patch adds support for new config option ipa_backup_server. The
description of this option's functionality is included in man page in
one of previous patches.
Primary server support: new option in AD provider

This patch adds support for new config option ad_backup_server. The
description of this option's functionality is included in man page in
one of previous patches.
Added unit test for sysdb_ssh.c
Require and call ldconfig from subpackages if appropriate

The SSSD subpackages were not calling ldconfig even though they contain
shared libraries.
Fix bad check
First-boot sss_seed tool
Change subdomain_info

Rename the structure to use a standard name prefix so it is properly
name-spaced, in preparation for changing the structure itself.
tests: Remove useless consts

Declaring a bunch of structures as const and then wrapping all uses in
discard_const_p() is a bit silly. Remove all these useless decorations.
80 columns police
Fix double semi-colons