IBM, and the white books, say this is working as designed.
• If LDAP dies, dsmserv stays up without it.
• If LDAP dies, and dsmserv restarts, it refuses to come up.
• ANR3103E https://www.ibm.com/support/knowledgecenter/SSEQVQ_8.1.5/srv.msgs/b_msgs_server.pdf
• Workaround is remove LDAPURL from dsmserv.opt, or wait for LDAP to become accessible.

On a multi-homed server, any links serving LDAP should be fault tolerant.

Any server using LDAP should have fault tolerant LDAP servers.

Here’s where to vote on getting the start-up limitation changed.
http://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=121985