[crankshaft] Fix interceptor shadowing constant global property.

[crankshaft] Fix interceptor shadowing constant global property.

This makes sure Crankshaft respects interceptors in the global object
even when they shadow a constant global property.

R=verwaest@chromium.org
TEST=cctest/test-api-interceptors/PrePropertyHandler

Review URL: https://codereview.chromium.org/1070803002

Cr-Commit-Position: refs/heads/master@{#27733}