Re: [libvirt] PATCH: Fix XM driver handling of disks without source file

It is possible for disks to be listed without a source file against them, eg a CDROM device with no media loaded. The XenD driver handles this, but the XM driver incorrectly generates XML with a <source file=''/> element instead of omitting the element entirely. This causes a bogus SXEXPR to be sent to XenD when starting the domain. This patch does three things - Makes the generic domain_conf.c XML parser accept XML docs with a bogus <source file=''/> and convert the source to NULL, instead of passing along the empty string "". This protects against broken apps - Makes the XM driver correctly generate XML in the first place, so omitting the <source> tag entirely. This is the root cause fix - Adds a test case for the XM driver to validate handling of devices with a source file