Merge pull request #8921 from davidflanagan/bug856798

Bug 856798: grant storage permission to mediadb and async storage clients r=fabrice(cherry picked from commit a1c8f555cdab3ed88860b4b0dfbd189f4bb36d20)
Merge pull request #8923 from davidflanagan/bug856798-v1-train

Merge pull request #8921 from davidflanagan/bug856798