functional-tests: Partially fix writeback tests

Use the new way of getting tracker-extract output, as the old way does not work.

Wait for writeback to be done by waiting for the file's mtime to change, instead
of using time.sleep().

The writeback tests still fail at this point.
functional-tests: Improve the wait-for-change code in helpers.StoreHelper

Fixes a bug in await_resource_deleted() where it would stop waiting as soon
as any resource was deleted, even if it wasn't the correct one.

New get_resource_id() function which is useful when calling
await_resource_deleted().

Code is hopefully clearer too.
functional-tests: Await resource addition / removal properly in 300, 310, 600

The tracker_miner_fs_wait_for_idle() function is not a good way to
detect when something has changed. We should always be listening
to GraphUpdated instead.

Thanks to Martin Kampas who did some of this already in commit
853eb94d78aa269b3b1024c138387ead0c601080.
functional-tests: Allow waiting on a specific property, and fix tests that need this

Resources are created when the miner process sees them, but often we
want to wait until they have been processed by the extractor, too. We
can achieve that by waiting for the insertion of a specific triple that
we know is set by tracker-extract.

This required adding a new parameter to the await_resource_inserted()
function.

The 310-fts-indexing and the base writeback test have been fixed to make
use of this, instead of using tracker_miner_fs_wait_for_idle().
functional-tests: Remove all remaining 'wait for miner to be idle' calls

We are running against a clean data directory when run by 'test-runner.sh', so
the miner should not have any initial crawling work to do. Therefore the tests
don't need to wait for it to be idle before starting.

Test cases should use the await_resource_inserted() and
await_resource_deleted() methods as these are (in theory) reliable. Waiting for
the miner to go idle and hoping this means that the desired file was crawled
and extracted is not reliable at all.

This should hopefully make the tests robust enough to be run continuously
without random failures occuring.

The tracker_miner_fs_wait_for_idle() functions are gone forever!
functional-tests: Remove IgnoreNextUpdate wrapper, nobody should be using this
functional-tests: Clean up minertest base class
functional-tests: Clean up writebacktest base class
tracker-writeback: Remove broken code to set file attributes

Remove some code which tries to set attributes of a file which no
longer exists.

This code was added in the following commit:

    commit 16fe51de1e93016a122ab089b0e0201c18de7ebc
    Author: Philip Van Hoof <philip@codeminded.be>
    Date:   Wed Nov 9 12:56:59 2011 +0100

        tracker-writeback: Preserve file permissions

        Fixes NB#289953.

Seems that the intent was to preserve the permission bits of the
file after tracker-writeback rewrites it. The code already takes
care of this at the time the temporary file is created.
Merge branch 'sam/functional-test-fixes'