Add perl as an explicit dependancy of erp5testnode
Change rpm2cpio url to point to a fixed revision
increase slapos.libnetworkcache version, because slapos.recipe.build needs a recent version
Revert "Change rpm2cpio url to point to a fixed revision"

This reverts commit 5bde992d0f4a8b9fced624ff132f7c0846c5bcb8.