[ubuntu] fix sporadic build fails (#2091)

* fix apt-get update

* Improve diagnostic

* handle "IPC connect call failed"

* Handle not-existing tool

* final refactoring

* remove todo

* remove which

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

@@ -2,6 +2,6 @@
 
 prefix=/usr/local/bin
 
-for tool in apt apt-get apt-fast;do
+for tool in apt apt-get apt-fast apt-key;do
   sudo rm -f $prefix/$tool
 done