util: Improve error reporting from absolutePathFromBaseFile helper
util: Improve error reporting from absolutePathFromBaseFile helper

https://bugzilla.redhat.com/show_bug.cgi?id=874860

There are multiple reasons canonicalize_file_name() used in
absolutePathFromBaseFile helper can fail. This patch enhances error
reporting from that helper.
(cherry picked from commit ca043b8c061cee39aada6b6ae6e9ce28f94c02b5)

mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2