Disable debug in CI

Otherwise we end up with a huge dump that Travis even won't show in the
UI.

Author: zeenix

.travis.yml

@@ -4,7 +4,7 @@ language: go
 go:
   - 1.11.x
 env:
-  - GO111MODULE=on GOFLAGS=-mod=vendor LIBVIRT_DEFAULT_URI='qemu+unix:///session' TF_LIBVIRT_DISABLE_PRIVILEGED_TESTS=1 TF_LIBVIRT_RNG_DEV='/dev/random' TF_LOG=DEBUG
+  - GO111MODULE=on GOFLAGS=-mod=vendor LIBVIRT_DEFAULT_URI='qemu+unix:///session' TF_LIBVIRT_DISABLE_PRIVILEGED_TESTS=1 TF_LIBVIRT_RNG_DEV='/dev/random'
 git:
   depth: 1
   go_import_path: github.com/dmacvicar/terraform-provider-libvirt