Add error checking to location load in endpoints service

[slevenick]

Fixes: hashicorp/terraform-provider-google#6840

Release Note Template for Downstream PRs (will be copied)

endpoints: Fixed a crash when `google_endpoints_service` is used on a machine without timezone data

[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, 5 insertions(+), 1 deletion(-))
Terraform Beta: Diff ( 1 file changed, 5 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=135154"