test: Prevent agressive teardown of the system during journal test
test: Prevent agressive teardown of the system during journal test

It seems we're losing log lines during reboot, and some tests
are failing because of that. Lets sync the disk before rebooting.

Fixes issues like:

	File "check-journal", line 215, in testBasic
  	  [ "check-journal", "BEFORE BOOT", "" ]

Closes #3529

Reviewed-by: Dominik Perpeet <f7830b2723a5db4fc185058b06cfab4b89a38da9@redhat.com>

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