Improve GPG key validation for release verification script.
Improve GPG key validation for release verification script.

Reviewed at https://reviews.apache.org/r/33997/

kidaa/aurora,shahankhatch/aurora,medallia/aurora,wfarner/aurora,apache/aurora,thinker0/aurora,protochron/aurora,rdelval/aurora,protochron/aurora,mschenck/aurora,thinker0/aurora,wfarner/aurora,crashlytics/aurora,kidaa/aurora,crashlytics/aurora,protochron/aurora,medallia/aurora,medallia/aurora,thinker0/aurora,apache/aurora,mschenck/aurora,rosmo/aurora,shahankhatch/aurora,mschenck/aurora,thinker0/aurora,shahankhatch/aurora,crashlytics/aurora,protochron/aurora,wfarner/aurora,rdelval/aurora,apache/aurora,crashlytics/aurora,shahankhatch/aurora,medallia/aurora,rdelval/aurora,shahankhatch/aurora,thinker0/aurora,shahankhatch/aurora,rosmo/aurora,rdelval/aurora,rosmo/aurora,mschenck/aurora,crashlytics/aurora,apache/aurora,mschenck/aurora,kidaa/aurora,protochron/aurora,thinker0/aurora,rdelval/aurora,wfarner/aurora,rosmo/aurora,medallia/aurora,wfarner/aurora,kidaa/aurora,rosmo/aurora,protochron/aurora,medallia/aurora,rosmo/aurora,apache/aurora,apache/aurora,crashlytics/aurora,kidaa/aurora,rdelval/aurora,wfarner/aurora,mschenck/aurora,kidaa/aurora