tests/salt: log more details about failures
tests/salt: log more details about failures

Log command output on failure. By default CalledProcessError
presentation do not include it.

QubesOS/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin