Update changelog for v1.16.0 release.
Update changelog for v1.16.0 release.

iphoting/healthchecks,iphoting/healthchecks,iphoting/healthchecks,iphoting/healthchecks,healthchecks/healthchecks,healthchecks/healthchecks,healthchecks/healthchecks,healthchecks/healthchecks