With XenServer 7.0 (XCP 2.1.0), VM live migration with iSCSI volume
will fail due to no relax_xsm_sr_check in /etc/xapi.conf in Dom0.
But since XS7.0, the default value of relax_xsm_sr_check is true if
not configured in /etc/xapi.conf in Dom0.
This fix is to add checks on XCP version, if it's equal or greater
than 2.1.0, will treat relax_xsm_sr_check=true if not found in
/etc/xapi.conf
Change-Id: I88d1d384ab7587c428e517d184258bb517dfb4ab
Closes-bug: #1610932
22b8ae0975