Fixes problems with incorrect method signatures related to shaded classes. For discussion see the jira issue.

Author: Elmer Garduno <elmerg@google.com>

Closes #3874 from elmer-garduno/fix_guava_signatures and squashes the following commits:

aa5d8e0 [Elmer Garduno] Unshade common/base[Function|Supplier] classes to fix guava methods signatures.