[ubuntu] Handle DNS error and errors in the child processes (#2146)

images/linux/scripts/base/apt-mock.sh

@@ -13,11 +13,10 @@ i=1
 while [ \$i -le 30 ];do
   err=\$(mktemp)
   $real_tool "\$@" 2>\$err
-  result=\$?
-  cat \$err >&2
 
-  # no errors, continue
-  test \$result -eq 0 && break
+  # no errors, break the loop and continue normal flow
+  test -f \$err || break
+  cat \$err >&2
 
   retry=false
 
@@ -30,6 +29,9 @@ while [ \$i -le 30 ];do
   elif grep -q 'IPC connect call failed' \$err;then
     # the delay should help with gpg-agent not ready
     retry=true
+  elif grep -q 'Temporary failure in name resolution' \$err;then
+    # It looks like DNS is not updated with random generated hostname yet
+    retry=true
   fi
 
   rm \$err