PluginVm: share files when RUNNING signal is received

Always share files when RUNNING signal is received
rather than only when we explicitly start.

Bug: b:135772268
Change-Id: I772284a51e1df32654ea2cb2ff4c9ddfe5df7152
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1674968
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Auto-Submit: Joel Hockey <joelhockey@chromium.org>
Reviewed-by: Timothy Loh <timloh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671969}