Fix some memory allocation errors:

* jail_setv will leak a parameter name if jailparam_import fails.
* jailparam_all loses the jailparam pointer on realloc error
  (a clear freshman mistake).
* If jailparam_init fails, the caller doesn't need to jailparam_free
  the buffer.  That's not really clear, so set things to NULL allowing
  jailparam_free to work without error (though it's still not required).