Description of problem:

After adding new LUNs on FC server, the LUNs are not detected on
hypervisors.

Version-Release number of selected component (if applicable):
All versions since 4.14.0

How reproducible:
Always

Steps to Reproduce:
1. Start a hypervisor connected to FC storage server
2. On the FC stoage server, add new LUN and expose it to the hypervisor
3. Try to edit a FC storage domain or create new one

Actual results:
The new LUN does not appear in the device lists

Expected results:
The new LUN should be listed

Additional info:

In versions before 4.14.0, we used to perform scsi scan, equivalent
to this:

    for path in /sys/class/scsi_host/host*/scan
        do echo "- - -" > $path
    done

This scan was removed in 66c24c1996 (iscsi: Iscsi rescan cleanup),
assuming that iscsiadm -m session --rescan is already doing the scsi
scan. iscsiadm is doing scssi scan, but only for iscsi connections.

This issue was reported in bug 1123637, but we did not detect the missing
scsi scan on FC devices. We fixed this but by introducing FC issue_lip
operation. This fix was disabled later due to bug 1157681, because on 
some storage server, issue_lip was disruptive.

Workaround:

Perform manual scsi scan on all fc hosts:
1. Log in to host
2. Run:

    for path in /sys/class/fc_host/host*/device/scsi_host/host*/scan; do
        echo "- - -" > $path
    done

For more details see: 
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Storage_Administration_Guide/scanning-storage-interconnects.html