Added configuration variable called boot_timeout

The hard-coded wait time of 2 for a server to be ready does not work for the smaller SmartOS server instances. Here, I have added a configuration variable to the provider in order to make the timeout configurable.
Added boot_time as an approved provider configuration variable.
Merge remote-tracking branch 'dekobon/master' into feature/boot-time-config

Conflicts:
	lib/vagrant-joyent/config.rb