Check for CA validity when verifying a certificate

In 'x509ca check', add an option to pass the CA certificate so that
the tool can verify that it actually signed the service
certificate (used to detect CA changes).
3 jobs for master in 20 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build Src
passed #3223
build:src

00:00:10

 
  Build Pkg
failed #3224
build:pkg

00:00:09

 
  Upload
skipped #3225
upload:pkg
 
Name Stage Failure
failed
build:pkg Build Pkg There is an unknown failure, please try again
Get:10 http://deb.debian.org/debian stretch-updates/main amd64 Packages 2018-05-05-2031.58.pdiff [329 B]
Get:11 http://deb.debian.org/debian stretch-backports/main amd64 Packages.diff/Index [27.8 kB]
Get:10 http://deb.debian.org/debian stretch-updates/main amd64 Packages 2018-05-05-2031.58.pdiff [329 B]
Get:11 http://deb.debian.org/debian stretch-backports/main amd64 Packages.diff/Index [27.8 kB]
Get:12 http://deb.debian.org/debian stretch-backports/main amd64 Packages [449 kB]
Reading package lists...
E: Could not open file /var/lib/apt/lists/deb.debian.org_debian_dists_stretch-backports_main_binary-amd64_Packages.diff_Index - open (2: No such file or directory)
ERROR: could not run 'apt-get update'
ERROR: Job failed: exit code 1