No longer necessary to have it, so remove it.

https://bugzilla.redhat.com/show_bug.cgi?id=1331552

Instead of disabling auto-login of all scsi targets (even those
that do not "belong" to libvirt), use iscsiadm's "--op nonpersistent"
during discovery of iSCSI targets (e.g. "iscsiadm --mode discovery
--type sendtargets") in order to avoid the node database being altered
which led to the need for the "large hammer" approach taken by
commit id '3c12b654'.

This commit removes the virISCSITargetAutologin adjustment (eg. the setting
of node.startup to "manual"). The iscsiadm command has supported this mode
of operation as of commit id 'ad873767' to open-iscsi.

Utilize the exit status parameter for virCommandRunRegex in order to
check the return error from the 'iscsiadm --mode session' command.
Without this enabled, if there are no sessions running then virCommandRun
would have displayed an error such as:

    2016-05-13 15:17:15.165+0000: 10920: error : virCommandWait:2553 :
               internal error: Child process (iscsiadm --mode session)
               unexpected exit status 21: iscsiadm: No active sessions.

It is possible that for certain paths (when probe is true) we only care
whether it's running or not to make certain decisions.  Spitting out
the error for those paths is unnecessary.

If we do have a situation where probe = false and there's an error,
then display the error from iscsiadm if it's there.

Rather than have virCommandRun just spit out the error, allow callers
to decide to pass the exitstatus so the caller can make intelligent
decisions based on the error.

https://bugzilla.redhat.com/show_bug.cgi?id=1172015

The refactoring done as part of commit id '59446096' caused a regression
for the multi initiator IQN commit '6aabcb5b' because the sendtargets was
not done on/for the initiator IQN prior to login (or trying to disable
autologin)

Prior to that commit, the paths were essentially

virStorageBackendISCSIStartPool
    virStorageBackendISCSILogin
        virStorageBackendISCSIConnection
            if initiatoriqn
                virStorageBackendCreateIfaceIQN
                Issue sendtargets
                Perform --login
            else
                Issue sendtargets
                Perform --login

After that commit:

virStorageBackendISCSIStartPool
    Issue sendtargets
    Call virStorageBackendISCSIConnection
        If initiatoriqn
            virStorageBackendCreateIfaceIQN
            Perform --login
        else
            Perform --login

So for non initiator IQN paths, nothing changed. For the initiator path,
the --login fails as does any attempts to change autologin via "--op update
--name node.startup --value manual".

Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

Remove the 'StorageBackend' from names of the functions and fix
indentation.