* Added a new members `Labels` to `FilterOptions struct`, and `EngineOptions` to
`HostListItem struct`. `HostListItems` is already being read from the file
store `config.json` which TestFilterHostsReturnSetLabel engine labels.
* Modified `parseFilters()` and added new `func matchesLabel(`) which compares
the one or more label values provided as input.
* Also the changes include added tests for UT and integration.
Note: Have kept `--filter label=<key>=<value>` syntax which is similar to
`docker images --filter` to keep the usability consistent.
review comments from @dgageot
Signed-off-by: Anil Belur <askb23@gmail.com>
0b0373d436