cluster: restore v0.10.x setupMaster() behaviour

In v0.10.x, process.argv and process.execArgv would only be
evaluated and copied into cluster.settings on the first call to
cluster.setupMaster() (either directly or via cluster.fork()),
allowing them to be modified as needed before initializing the
settings.

In 41b75ca the behaviour was changed so that these values are
initialized at the time of the first require('cluster').

Fixes #7670.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
test: regression test for cluser.setupMaster()

Tests for the behaviour in v0.10.x which allows process.argv changes
to be honoured by cluster.setupMaster().

Signed-off-by: Trevor Norris <trev.norris@gmail.com>