(POOLER-165) Fix purge_unconfigured_folders

[mattkirby]

This commit fixes the purge_unconfigured_folders feature to ensure that it can successfully identify folders and instances that are no longer used. Without this change the feature does not work as advertised.

[highb]

Tested this out on my docker-compose setup by adding a rando-calrissian folder with an Artisanal VM inside, vmpooler happily cleaned that up for me:

vmpooler_1    | [2020-04-07 16:56:28] starting vmpooler
vmpooler_1    | [2020-04-07 16:56:28] starting vmpooler
vmpooler_1    | [2020-04-07 16:56:28] [!] Creating provider 'vsphere-vc6'
vmpooler_1    | [2020-04-07 16:56:28] [!] Creating provider 'vsphere-vc6'
vmpooler_1    | [2020-04-07 16:56:28] [vsphere-vc6] ConnPool - Creating a connection pool of size 5 with timeout 60
vmpooler_1    | [2020-04-07 16:56:28] [vsphere-vc6] ConnPool - Creating a connection pool of size 5 with timeout 60
vmpooler_1    | [2020-04-07 16:56:28] [*] [disk_manager] starting worker thread
vmpooler_1    | [2020-04-07 16:56:28] [*] [disk_manager] starting worker thread
vmpooler_1    | [2020-04-07 16:56:28] [*] [snapshot_manager] starting worker thread
vmpooler_1    | [2020-04-07 16:56:28] [*] [snapshot_manager] starting worker thread
vmpooler_1    | [2020-04-07 16:56:28] [vsphere-vc6] Connection Pool - Creating a connection object
vmpooler_1    | [2020-04-07 16:56:28] [vsphere-vc6] Connection Pool - Creating a connection object
vmpooler_1    | [2020-04-07 16:56:28] [*] [centos-7-x86_64] starting worker thread
vmpooler_1    | [2020-04-07 16:56:28] [*] [centos-7-x86_64] starting worker thread
vmpooler_1    | == Sinatra (v2.0.8.1) has taken the stage on 4567 for production with backup from Puma
vmpooler_1    | The signal INFO is in use by the JVM and will not work correctly on this platform
vmpooler_1    | Puma starting in single mode...
vmpooler_1    | * Version 4.3.3 (jruby 9.2.9.0 - ruby 2.5.7), codename: Mysterious Traveller
vmpooler_1    | * Min threads: 0, max threads: 16
vmpooler_1    | * Environment: production
vmpooler_1    | * Listening on tcp://0.0.0.0:4567
vmpooler_1    | Use Ctrl-C to stop
vmpooler_1    | [2020-04-07 16:56:30] [vsphere-vc6] Connection Pool - Creating a connection object
vmpooler_1    | [2020-04-07 16:56:30] [vsphere-vc6] Connection Pool - Creating a connection object
vmpooler_1    | [2020-04-07 16:56:31] [-] [rando-calrissian] 'Artisanal VM' destroyed in 0.77 seconds
vmpooler_1    | [2020-04-07 16:56:31] [-] [rando-calrissian] 'Artisanal VM' destroyed in 0.77 seconds
vmpooler_1    | [2020-04-07 16:56:31] [-] [rando-calrissian] removing unconfigured folder
vmpooler_1    | [2020-04-07 16:56:31] [-] [rando-calrissian] removing unconfigured folder
vmpooler_1    | [2020-04-07 16:57:11] [!] [centos-7-x86_64] is empty
vmpooler_1    | [2020-04-07 16:57:11] [!] [centos-7-x86_64] is empty
vmpooler_1    | [2020-04-07 16:57:11] [ ] [centos-7-x86_64] Starting to clone 'erratic-keg'
vmpooler_1    | [2020-04-07 16:57:11] [ ] [centos-7-x86_64] Starting to clone 'erratic-keg'
vmpooler_1    | [2020-04-07 16:57:13] [+] [centos-7-x86_64] 'erratic-keg' cloned in 2.38 seconds
vmpooler_1    | [2020-04-07 16:57:13] [+] [centos-7-x86_64] 'erratic-keg' cloned in 2.38 seconds