Refactor: tools: Use cib_sync_call unconditionally in cibadmin

Previously, we maintained two code paths. In the default path, we made
an asynchronous request (for a live CIB) and ran a mainloop to await the
result. However, cibadmin can't exit until it gets the result, so this
asynchronous call behaved like a synchronous call.

Ref T817

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>