Reset internet availability check before each spec

Some specs run with WebMocks and mock no internet connection while
other specs, notably integration tests, run and access the internet.
Depending on the order of running of specs, an incorrect internet
availability is cached in a DownloadCache class variable. Reset the
cache before each spec.

[#59391214]
Merge 59391214-reset-internet-check to master

[Completes #59391214]