Inh most case we already have a record from before, so avoid doing a useless
lookup in the database.
In owncloudpropagator.cpp, directories do not have a checksum so no need
to call a function that preserves it
Since we do not recurse within some directories, many files are not seen.
The stale entry will cleanup by themself as the sync engine try to remove
the files that are already removed.
Should we need to actually do this cleanup, it should be dotected in the
discovery.
Conflicts:
src/csync/csync_reconcile.cpp
src/csync/csync_update.cpp
src/libsync/syncengine.cpp
src/libsync/syncengine.h
Note: csync changes from 5e442f588e
are not included and will be fixed separately
Add a test to test the data fingerprint feature make me realize it was broken.
The code was relying in the distinction between empty and null QByteArray,
but this was a bad idea as this difference is lost when going through QString.
The problem here is that we were sometimes allocating the error_string with
qstrdup, which need to be released with delete[] and not free().
Simplify the code by using QString instead.
```
==7230== Mismatched free() / delete / delete []
==7230== at 0x4C2E10B: free (vg_replace_malloc.c:530)
==7230== by 0x57C2321: csync_s::reinitialize() (csync.cpp:247)
==7230== by 0x548130F: OCC::SyncEngine::finalize(bool) (syncengine.cpp:1212)
==7230== by 0x5481223: OCC::SyncEngine::handleSyncError(csync_s*, char const*) (syncengine.cpp:746)
==7230== by 0x5483E78: OCC::SyncEngine::slotDiscoveryJobFinished(int) (syncengine.cpp:965)
==7230== by 0x5495E34: QtPrivate::FunctorCall<QtPrivate::IndexesList<0>, QtPrivate::List<int>, void, void (OCC::SyncEngine::*)(int)>::call(void (OCC::SyncEngine::*)(int), OCC::SyncEngine*, void**) (qobjectdefs_impl.h:134)
==7230== by 0x5495D92: void QtPrivate::FunctionPointer<void (OCC::SyncEngine::*)(int)>::call<QtPrivate::List<int>, void>(void (OCC::SyncEngine::*)(int), OCC::SyncEngine*, void**) (qobjectdefs_impl.h:167)
==7230== by 0x5495CB5: QtPrivate::QSlotObject<void (OCC::SyncEngine::*)(int), QtPrivate::List<int>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) (qobjectdefs_impl.h:396)
==7230== by 0xA9BF2E1: QObject::event(QEvent*) (in /usr/lib/libQt5Core.so.5.11.0)
==7230== by 0x64BE983: QApplicationPrivate::notify_helper(QObject*, QEvent*) (in /usr/lib/libQt5Widgets.so.5.11.0)
==7230== by 0x64C625A: QApplication::notify(QObject*, QEvent*) (in /usr/lib/libQt5Widgets.so.5.11.0)
==7230== by 0xA994BC8: QCoreApplication::notifyInternal2(QObject*, QEvent*) (in /usr/lib/libQt5Core.so.5.11.0)
==7230== Address 0x225b2640 is 0 bytes inside a block of size 50 alloc'd
==7230== at 0x4C2DC6F: operator new[](unsigned long) (vg_replace_malloc.c:423)
==7230== by 0xA7E8FC8: qstrdup(char const*) (in /usr/lib/libQt5Core.so.5.11.0)
==7230== by 0x53F5750: OCC::DiscoveryJob::remote_vio_opendir_hook(char const*, void*) (discoveryphase.cpp:666)
==7230== by 0x57E1278: csync_vio_opendir(csync_s*, char const*) (csync_vio.cpp:39)
==7230== by 0x57D718F: csync_ftw(csync_s*, char const*, int (*)(csync_s*, std::unique_ptr<csync_file_stat_s, std::default_delete<csync_file_stat_s> >), unsigned int) (csync_update.cpp:674)
==7230== by 0x57C1B05: csync_update(csync_s*) (csync.cpp:109)
==7230== by 0x53F5BCC: OCC::DiscoveryJob::start() (discoveryphase.cpp:718)
==7230== by 0x54B8F74: OCC::DiscoveryJob::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (moc_discoveryphase.cpp:494)
==7230== by 0xA9BF2E1: QObject::event(QEvent*) (in /usr/lib/libQt5Core.so.5.11.0)
==7230== by 0x64BE983: QApplicationPrivate::notify_helper(QObject*, QEvent*) (in /usr/lib/libQt5Widgets.so.5.11.0)
==7230== by 0x64C625A: QApplication::notify(QObject*, QEvent*) (in /usr/lib/libQt5Widgets.so.5.11.0)
==7230== by 0xA994BC8: QCoreApplication::notifyInternal2(QObject*, QEvent*) (in /usr/lib/libQt5Core.so.5.11.0)
==7230==
```
