Failed to initialize connection

Failed to initialize connection

Failed to initialize connection when the storage server heavy loading.
Changed related on:
  dpl_iscsi and dpl_fc
    initialize_connection
    terminate_connection

When storage server busy, the request api will receive httplib response
code accepted and the response body include event uuid. The operation
request use the event uuid to comfirm the job is completed or not.

Change-Id: I4ad8283d355d6b53390e69123ed7b3ed873d4c4e
Closes-Bug: 1357635