(maint) Fix using ABS service without a .vmfloaty.yml file

[cthorn42]

If you do not use a config file, and define everything on the command line,
previously the service always defaulted to vmpooler. Even if you requested ABS.
This PR fixes that, now we'll see if the config has no service defined and we
defined on the command line a service, we'll use that service.

Reviewers

@puppetlabs/dio
@highb
@briancain

[cthorn42]

With current vmfloaty trying to use ABS and no config file fails:

floaty get --service=abs --user=chirstopher.thorn --token=<cut out> centos-7-x86_64 --url=https://cinext-abs.delivery.puppetlabs.net/api/v2 --trace

WARNING: There was no config file at /Users/cthorn/.vmfloaty.yml
Traceback (most recent call last):
	11: from /Users/cthorn/repo/vmfloaty/bin/floaty:8:in `<main>'
	10: from /Users/cthorn/repo/vmfloaty/lib/vmfloaty.rb:462:in `run'
	 9: from /Users/cthorn/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/commander-4.5.2/lib/commander/delegates.rb:15:in `run!'
	 8: from /Users/cthorn/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/commander-4.5.2/lib/commander/runner.rb:68:in `run!'
	 7: from /Users/cthorn/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/commander-4.5.2/lib/commander/runner.rb:452:in `run_active_command'
	 6: from /Users/cthorn/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/commander-4.5.2/lib/commander/command.rb:155:in `run'
	 5: from /Users/cthorn/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/commander-4.5.2/lib/commander/command.rb:184:in `call'
	 4: from /Users/cthorn/repo/vmfloaty/lib/vmfloaty.rb:68:in `block (2 levels) in run'
	 3: from /Users/cthorn/repo/vmfloaty/lib/vmfloaty/service.rb:81:in `retrieve'
	 2: from /Users/cthorn/repo/vmfloaty/lib/vmfloaty/pooler.rb:44:in `retrieve'
	 1: from /Users/cthorn/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/json-2.3.1/lib/json/common.rb:263:in `parse'
/Users/cthorn/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/json-2.3.1/lib/json/common.rb:263:in `parse': 784: unexpected token at 'POST /api/v2/vm/centos-7-x86_64' (JSON::ParserError)

Note in the stack trace on line 2, we're using pooler.rb, where we should be using abs.rb.

With this PR I can now checkout a vm with ABS:

floaty get --service=abs --user=chirstopher.thorn --token=<cut out> centos-7-x86_64 --url=https://cinext-abs.delivery.puppetlabs.net/api/v2

WARNING: There was no config file at /Users/cthorn/.vmfloaty.yml
Requesting VMs with job_id: 1597940546886.  Will retry for up to an hour.
<cutting out 16 attempts>
Waiting 10 seconds to check if ABS request has been filled.  Queue Position: 383... (x17)
- key-hollowware.delivery.puppetlabs.net (centos-7-x86_64)

[briancain]

Thanks for the fixes @cthorn42 ! :) 👍