Move casd local cache directory in e2e temporary directory
Due to buildbox-casd
returning a non 200 return code when trying to write an already existing blob, and the e2e test script not cleaning up the local cache directory, builds of this are failing. Move the casd local cache directory into the e2e temporary directory, which gets removed at the end of the e2e test script.
We do need to revisit buildbox-casd returning ALREADY_EXISTS
when writing an already existing blob though.