Fix inverted logic in Chrome PFQ.
Fix inverted logic in Chrome PFQ.

Currently the Chrome PFQ actually does the opposite of what we want,
and only exits early when there is a new Chrome. This needs to be
inverted.

Besides this, we also need to skip this logic on builders other than
the Chrome PFQ (e.g. branch builders).

BUG=none
TEST=Trybot run of Chrome PFQ.

Change-Id: I200a2edb0f0a944f4fbadaf1d39a794d3da15a57
Reviewed-on: https://gerrit.chromium.org/gerrit/46801
Reviewed-by: Ryan Cui <5ce1592d53754a87a44fc2eb7b63d5f77cf50fdb@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite