store/java: invalid JAVA_HOME paths and files

[adamdecaf]

I was running into some issues with a modified JAVA_HOME file layout.

1. Using the wrong password didn't seem to be caught. I had other changes locally, but cert-manage just hung...

$ ./bin/keytool -list -storepass <pass> -keystore <path>/lib/security/cacerts -rfc
keytool error: java.io.IOException: Keystore was tampered with, or password was incorrect

2. If kpath's value was a directory cert-manage seemed to hang.

3. $JAVA_HOME/lib/security/cacerts didn't exist and cert-manage hung.