This will be validated in the ssi branch and merged into master later.

The code in this part was uselessly taking exclusive root locks, leading to locking
fights when starting all drive as the same time in bigger systems.

This happens when the notification is received multiple times. This did not show
before full scale test.

The locking is now handled in a single function.
This functions is also used in the asynchronous operations. This operations have
been simplified in this operation: we now do a synchronous stat after the locking.
Previously stat was the first asynchronous operation. This will slightly slow down
the async operations (for the gain of code simplicity).

This commit only replaces backoff with notifications in exclusive locks, for validation
with a multithreaded unit test. This proof of concept is considered as working, as the
measured gap between a lock release and a lock take never exceeds ~1/4 of a second, with a typical
release-lock gap in the few ms to few tens of ms.

Done.

Replaced set_target_properties( .. .. INSTALL_RPATH ..) with set_property (TARGET .. APPEND PROPERTY INSTALL_RPATH ..)

The problem happened in tests when the object we deleted by hand. This commit
prevents a crash in this (already pathological) situation.

Also added more information to the logs.

To handle cta_admin ar ls

This reverts commit 35a0cf48.

This is a first version of the command which has a fixed-size return buffer,
this code still needs to be refactored to allow a result of arbitrary size.

Removes the log parameter from ListArchiveFilesCmd constructor. Elsewhere we
are using log context objects: the SSI version of the command dispatcher has
access to the lc but not the log object. In any case this was not being used
so safe to remove for the time being.

We do not do a stat before reading. Instead we ask for an arbitrarily big read, and find out
the size of the data while reading. This avoids a race condition in lockfree reads where we failed
to get the full object if it got re-written to a bigger size between stat an read.

Signed-off-by: Cristina Moraru <cristina-gabriela.moraru@cern.ch>

Signed-off-by: Cristina Moraru <cristina-gabriela.moraru@cern.ch>