Update RBE credential location (#64)

Update RBE credential location

Author: flyingsilverfin

.bazelrc

@@ -9,8 +9,8 @@ build:rbe --remote_cache=cloud.buildbuddy.io
 build:rbe --remote_executor=cloud.buildbuddy.io
 build:rbe --bes_backend=cloud.buildbuddy.io
 build:rbe --bes_results_url=https://app.buildbuddy.io/invocation/
-build:rbe --tls_client_certificate=/home/circleci/.credentials/buildbuddy-cert.pem
-build:rbe --tls_client_key=/home/circleci/.credentials/buildbuddy-key.pem
+build:rbe --tls_client_certificate=/opt/.credentials/buildbuddy-cert.pem
+build:rbe --tls_client_key=/opt/.credentials/buildbuddy-key.pem
 build:rbe --host_platform=@graknlabs_dependencies//image/rbe:ubuntu-1604
 build:rbe --platforms=@graknlabs_dependencies//image/rbe:ubuntu-1604
 build:rbe --extra_execution_platforms=@graknlabs_dependencies//image/rbe:ubuntu-1604