qemuDomainNamespaceUnlinkPaths: Turn @paths into string list

qemuDomainNamespaceUnlinkPaths: Turn @paths into string list

So far, the only caller qemuDomainNamespaceUnlinkPath() will
always pass a single path to unlink, but similarly to
qemuDomainNamespaceMknodPaths() - there are a few callers that
would like to pass two or more files to unlink at once (held in a
string list). Make the @paths argument a string list then.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>