912776: use cfg.get_int for proxy port

Use get_int for proxy_port config lookups where
it need to be an integeer (ie, all cases except
where it is being used to create a string)
912776: use config.get_int for server port as well

Require python-rhsm >= 1.8.6 to have the config.get_int
912776: cast port numbers from cli to int immediately
912776: fix migration test scripts to expect get_int usage
Remove use of _add_common_options in cli command sub classes

Some cli classes were using _add_common_options to add
any cli parser options, where they should just do this
in the init.
Merge pull request #520 from candlepin/alikins/912776_proxy_port_int

Alikins/912776 proxy port int
mock stdout.isatty expected args, but no args are required
Merge pull request #521 from candlepin/alikins/uncommon_options

Remove use of _add_common_options in cli command sub classes
Merge pull request #522 from candlepin/alikins/isatty

mock stdout.isatty expected args, but no args are required
Merge branch 'master' into alikins/plugins