do not fail acceptance test when provider returns a warning

[bcmdarroch]

🛠️ Description

Quick fix. During the Preconfig step (prior to plan or apply), the HCP provider checks the HCP status page and returns a warning if there is any degraded performance or outage. The acceptance tests were exiting on any error during the preconfig step, so it was failing on the status page warnings. This PR checks the Severity of the returned error (type Diagnostic) and allows tests to proceed despite any warnings.

Output from acceptance testing:

$ make testacc TESTARGS='-run=Packer'

--- PASS: TestAcc_dataSourcePacker (7.36s)
--- PASS: TestAcc_dataSourcePacker_revokedIteration (9.72s)
--- PASS: TestAcc_dataSourcePackerImage (6.20s)
--- PASS: TestAcc_dataSourcePackerImage_revokedIteration (8.97s)
--- PASS: TestAcc_dataSourcePackerImage_channelAndIterationIDReject (2.35s)
--- PASS: TestAcc_dataSourcePackerImage_channelAccept (4.64s)
--- PASS: TestAcc_dataSourcePackerIteration (4.27s)
--- PASS: TestAcc_dataSourcePackerIteration_revokedIteration (9.83s)
--- PASS: TestAccPackerChannel (7.19s)
--- PASS: TestAccPackerChannel_AssignedIteration (6.43s)
--- PASS: TestAccPackerChannel_UpdateAssignedIteration (9.97s)
--- PASS: TestAccPackerChannel_UpdateAssignedIterationWithFingerprint (4.83s)
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/provider	82.386s

[nywilken]

Nice catch! 🚀