spec: switch to use rpm conditional switches
spec: switch to use rpm conditional switches

Rpmbuild supports conditional package builds with the command line
switches --with and --without.

More detail please see [1].

[1]: https://rpm.org/user_doc/conditional_builds.html

Signed-off-by: Xiubo Li <d6cd9ec469dfb11098caa077ea0b7b3220fc70dc@redhat.com>

agrover/tcmu-runner,open-iscsi/tcmu-runner,open-iscsi/tcmu-runner