silx.io.h5py_utils.File: avoid emitting several time warning if incoherent hdf5 / h5py locking argument

[payno]

avoid emitting several time warning if incoherent hdf5 / h5py locking argument.
Done with a decorator to try to improve readability

[payno]

I have to admit I am a bit uncertain about this PR.
To be considered:
* If users have particular version on h5py / hdf5 en get incoherent locking parameter we will get a tone of warning at the moment. But the class will hardly failed. (as expressed in the warning). So it might be not that bad that logs are filled with the error.
* but some users knowing very well what they are doing might that this cumbersome. But do we have such users ?
* This will increase complexity of the class (I did a decorator to try to reduce it). Not sure if I succeed.

[t20100]

Provided it's a critical log message and the issues we have with HDF5 file locking, I'm not sure making this log quiet is a good idea.

What could be improved is that the message is logged without checking if locking is actually disabled, so moving the log below and checking the value of locking would save a few unwanted messages.

[t20100]

You could (ab)use functools.lru_cache here and save the global variable

[t20100]

I agree this makes it more complicated to have a function to log a specific message

[payno]

Agree, let close this one for the moment and we might rethink it later.