Add support for iocage instead of jexec

[fungalcofe]

I create Jails with iocage.
jexec don't work with jail hostname when it's created from iocage.

Edit changed priority:
iocage > jailme > jexec

[austinhyde]

Besides the requested spelling/formatting...

I haven't used iocage, but as far as I can tell you need to run iocage exec <jail> <command ...>, whereas the existing usage runs <jailme|jexec> <jail> <command ...> (no exec subcommand`).

There's a few things we could do, like set self.connector to "iocage exec" instead of just iocage, or add a switch in exec_command that maps self.connector to the correct invocation.

Could you please double check that and make any required changes?

[austinhyde]

Just some minor spelling/formatting suggestions:

Suggested change

	Another alternavite to requering root acces is to use the [`iocage`](https://www.freshports.org/sysutils/iocage/) utility.
	`iocage` is a "jail/container manager amalgamating some of the bestfeatures and technologies the FreeBSD operating system has to offer"
	If you want to use `jailme` or `iocage`, you'll need to ensure it's installed on the jailhost, and specify the user to `sudo` as
	via `--become-user` on the command line, or `become_user: username` in a play or task. sshjail will prefer to use `jailme`
	if it's installed, whether you are sudoing as root or not.
	Another alternative to requiring root access is to use the [`iocage`](https://www.freshports.org/sysutils/iocage/) utility.
	`iocage` is a "jail/container manager amalgamating some of the best features and technologies the FreeBSD operating system has to offer"
	If you want to use `jailme` or `iocage`, you'll need to ensure it's installed on the jailhost, and specify the user to `sudo` as
	via `--become-user` on the command line, or `become_user: username` in a play or task.
	sshjail will prefer to use `iocage`, then `jailme` if they are installed, whether you are sudoing as root or not.