Fix shadow on fab + all rounded edges

Shadow on rounded edges were broken. Some views (specially fab) can have
rounded edges without specifying path, but in shadow code we relied
heavily on existance of path to determine if this vector drawable.

This fix allows any rounded edges to be acceptable.

Bug: 119754361
Test: Local test (RenderTests) all passes. +
https://screenshot.googleplex.com/9r0Q54HQJ7U

Change-Id: I9c88a0d0ef5f27ef2aeb41622572872e1fdc30b0
(cherry picked from commit 0621bab924d1798c9e5584f1c146d3f663c2fa58)