Implement concurrent requests call to the apic

[thenodon]

Describe the solution you'd like
In the current implementation all requests to the ACI APIC is done sequentially. The scrape time will be the sum of all the requests. Instead goroutines should be used for each http request and the response returned on a channel(s). Depending on the parallelism of the machine the scrape time would be in the range of the time of the longest response time of all the request done to the APIC.

This will have a little effect on scrape time if the number of APIC queries are low, but will have a major effect on scrape time when the number increase and keep the scrape time more "constant" to a growing number of queries.

[thenodon]

At 17:41 switch to use concurrent APIC request.