(QENG-762) add support to beaker scp_to/scp_from to ignore files of ...

... certain name/type

- added support to scp_to for an ignore list of files/dirs.  Does not
  support globbing.
`options[:ignore]` is a String, but is used in boolean situations. A new variable for usage in `if` evaluations would allow a more appropriate variable name and permit basic sanity checks on the provided String.

```ruby
has_ignore = options[:ignore] && !options[:ignore].empty?

if has_ignore
    ignore_arr = ...
    ...
end
```