Added opportunity to define iscsi_helper and scheduler_default_filters params.

Change-Id: I1175f2e8050c1b979a9ad9fd8bcd3072bcb44f4c
Related-PROD: PROD-25448
diff --git a/cinder/files/backend/_lvm.conf b/cinder/files/backend/_lvm.conf
index e305056..db24344 100644
--- a/cinder/files/backend/_lvm.conf
+++ b/cinder/files/backend/_lvm.conf
@@ -6,5 +6,5 @@
 {%- if backend.lvm_type is defined %}
 lvm_type = {{ backend.lvm_type }}
 {%- endif  %}
-iscsi_helper = tgtadm
-volume_group = {{ backend.volume_group }}
\ No newline at end of file
+iscsi_helper = {{ backend.get('iscsi_helper', 'tgtadm') }}
+volume_group = {{ backend.volume_group }}