On IRC, Hydrar pointed a problem where 'virsh edit' failed on
his domain created through an ISCSI pool managed by virt-manager,
all because the XML included a block device with colons in the
name.
* docs/schemas/basictypes.rng (absFilePath): Add colon as safe.
* tests/qemuxml2argvdata/qemuxml2argv-disk-iscsi.xml: New file.
* tests/qemuxml2argvdata/qemuxml2argv-disk-iscsi.args: Likewise.
* tests/qemuxml2argvtest.c (mymain): Test it.
Signed-off-by: Eric Blake <eblake@redhat.com>