Fix compatibility with Pulsar 3.3.x+ docker images where /pulsar isn't writable

[lhotari]

Motivation

Fixes this issue:

[pod/pulsar-ci-zookeeper-0/pulsar-ci-zookeeper] pkcs12: Can't open "/pulsar/zookeeper.p12" for writing, Permission denied
[pod/pulsar-ci-zookeeper-0/pulsar-ci-zookeeper] Importing keystore /pulsar/zookeeper.p12 to /pulsar/zookeeper.keystore.jks...

Modifications

Use a temporary directory to store the keystore files.

Verifying this change

• Make sure that the change passes the CI checks.

Additional context

• requires [improve] Install openssl in the docker image to fix compatibility with Apache Pulsar Helm chart pulsar#23362 changes on Pulsar side to add openssl to the image.