container.go: rename run's 'host' config to be hostname (as in docker cmd)
container.go: rename run's 'host' config to be hostname (as in docker cmd)

it's unexpected to have crane use 'host' as the name of the config
to assign the containers hostname when docker uses 'hostname'.  And
we already had several crane files using 'hostname' expecting that
to work.  SO, renamed it

ScientificRevenue/crane