[component_manager] Loosen flags checks

Disallow unknown flags, rather than requiring precise matches.

Bug: 103363
Change-Id: I40aa6cda45f78ea86cfea61cb8d2ac7d5ccadc7a
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/694802
Reviewed-by: Stephen Demos <sdemos@google.com>
Fuchsia-Auto-Submit: Tamir Duberstein <tamird@google.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
Reviewed-by: Luke Nicholson <lukenicholson@google.com>