oo-install: Fix bail code for scp in run_on_host

Properly define the `bail` proc in `run_on_host` so that it actually does bail if the `scp` command fails, rather than continuing execution.

The semantics of procs defined using the `proc` keyword changed between Ruby 1.8.7 and Ruby 1.9.3.  In 1.8.7, a `return` statement in a proc defined using the `proc` keyword does not return from the caller, which is what is intended in the `bail` proc.  It is necessary to use `Proc.new` instead, which behaves as expected on both Ruby 1.8.7 and Ruby 1.9.3.

This commit fixes bug 1092108.