site.httpport for ubuntu diskless support

[immarvin]

The PR is to fix issue found by autotest on ubuntu diskless support

UT:

root@c910f03c09k03:/opt/xcat/share/xcat/tools/autotest/bundle# xcattest -b ./non_default_http_port_test.bundle   -f /opt/xcat/share/xcat/tools/autotest/default.conf
...
------END::clean_up_env::Passed::Time:Mon Dec 17 04:02:10 2018 ::Duration::366 sec------
------Total: 14 , Failed: 0------

xCAT automated test finished at Mon Dec 17 04:02:10 2018
Please check results in the /opt/xcat/bin/../share/xcat/tools/autotest/result/,
and see /opt/xcat/bin/../share/xcat/tools/autotest/result//failedcases.20181217032903 file for failed cases.
see /opt/xcat/bin/../share/xcat/tools/autotest/result//performance.report.20181217032903 file for time consumption

[zet809]

Good to me, I agree to merge. Thx @immarvin