Fix: tools: restore crmadmin default timeout to 30 seconds

Regression introduced in 2.1.5 via a6ec43e

That commit switched to using synchronous (blocking) IPC when timeout
was set to 0 (the default, which previously meant use 30s). That was
a change in behavior that was a bad idea if someone is calling it in a
script.

This still allows the user to explicitly specify --timeout=0 to get the
blocking behavior.