Move Dialer to top level variable
Move Dialer to top level variable

- Initializing the Dialer inside New causes few additional seconds of
performance overhead. (Tested with `bosh vms` and `bosh env`)

Signed-off-by: Tom Viehman <ef9e7682e71c138189ac51545830b782ff2b8b7d@pivotal.io>

cloudfoundry/bosh-utils,cloudfoundry/bosh-utils