Set context early on in LoadAndValidate to prevent NPE

[slevenick]

I do not know that this will fix the problem, but I believe it will. Cannot reproduce crash locally even though context is verified to be nil going in to creds, err := googleoauth.CredentialsFromJSON(c.context, []byte(contents), clientScopes...)

Release Note Template for Downstream PRs (will be copied)

Fixed crash due to nil context when loading credentials

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 2 insertions(+), 1 deletion(-))
Terraform Beta: Diff ( 1 file changed, 2 insertions(+), 1 deletion(-))
TF Conversion: Diff ( 1 file changed, 2 insertions(+), 1 deletion(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=136752"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccActiveDirectoryDomain_activeDirectoryDomainBasicExample|TestAccActiveDirectoryDomain_update|TestAccComputeRouterInterface_withTunnel|TestAccComputeRouterInterface_basic|TestAccEndpointsService_basic|TestAccHealthcareDicomStore_basic You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=136753"