Define an osd_dev_info structure that Uniquely identifies an OSD
device lun on the network. The identification is built from unique
target attributes and is the same for all network/SAN machines.

osduld_info_lookup() - NEW
    New API that will lookup an osd_dev by its osd_dev_info.
    This is used by pNFS-objects for cross network global device
    identification.

osduld_device_info() - NEW
    Given an osd_dev handle returns its associated osd_dev_info.
    This is used by exofs to encode the device information for
    network clients. (Get-device-info). The ULD fetches this
    information at startup and hangs it on each OSD device. (This is
    a fast operation that can be called at any condition)

osd_auto_detect_ver() - REVISED
    Now returns an osd_dev_info structure. Is only called once
    by ULD as before. See added comments for how to use.
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>