Convert networkDnsmasqLeaseFileName to a replaceable function pointer
that allow the testsuite to use a version of that function that is not
depending on configure --localstatedir.
This fixes 5 of 6 test failures, when configure --localstatedir isn't
set to /var.
The dnsmasq commandline was being built as a part of running
dnsmasq. This patch puts the commandline build into a separate
function (and exports it as a private API) making it possible to build
a dnsmasq commandline without executing it, so that we can write a
test program to verify that the proper commandlines are being created.
Signed-off-by: Michal Novotny <minovotn@redhat.com>
