The `aws_availability_zones` data source test was panicking. This fixes both tests
```
$ make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSAvailabilityZones'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/01/31 15:47:39 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSAvailabilityZones -timeout 120m
=== RUN TestAccAWSAvailabilityZones_basic
--- PASS: TestAccAWSAvailabilityZones_basic (12.56s)
=== RUN TestAccAWSAvailabilityZones_stateFilter
--- PASS: TestAccAWSAvailabilityZones_stateFilter (13.59s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 26.187s
```
This commit is a maintenance change aimed at aligning file names so that they
fall in line with the established naming convention.
Signed-off-by: Krzysztof Wilczynski <krzysztof.wilczynski@linux.com>
Jake Champlin