Allow to define multiple LDAP servers for one location

Actual behavior

Connection fails if mutliple LDAP servers are defined for one location.

Expected behavior

FD should be able to move on next LDAP server if the first fails, or simple pass the server array in ldap_connect function to let PHP LDAP manage it

Step by step description of new behaviour

Configure several referrals like this:

    <location name="example-ha">
            <referral URI="ldap://ldap-example-1.local/dc=example,dc=com"
                        adminDn="cn=fusiondirectory,ou=dsa,dc=example,dc=com"
                        adminPassword="secret" />
            <referral URI="ldap://ldap-example-2.local/dc=example,dc=com"
                        adminDn="cn=fusiondirectory,ou=dsa,dc=example,dc=com"
                        adminPassword="secret" />
    </location>

Or defined serveral LDAP servers in one referral, like this:

    <location name="example-ha">
            <referral URI="ldap://ldap-example-1.local/dc=example,dc=com ldap://ldap-example-2.local/dc=example,dc=com"
                        adminDn="cn=fusiondirectory,ou=dsa,dc=example,dc=com"
                        adminPassword="secret" />
    </location>

Benefits

FD will handle failover, allowing to switch to next LDAP server when the first is down

Possible Drawbacks

FD will not be responsible for data consistency when dead LDAP come to life