test: Move the pool's name define to the header
test: Use the pre-defined default tests pool in the Pools UT
Remove getDirPath definition from RadosFsPriv

It was mistakenly defined in there.
Remove the use of a set for the pools' prefixes
Fix creating files when there is no ioctx

It now returns -ENODEV.
Fix calling update on RadosFsInfo with no ioctx

It was crashing because this case was not being considered.
test: Create a file and dir when no pool is set
Add an addMetadataPool to RadosFs

For this, the addPool method in RadosFsPriv is now more generic,
accepting the pools map and mutex to which the new pool should
be added.
Make RadosFsPriv::addPool accept the pool and mutex

This is so it can be used for adding a data pool as well as a metadata
one.
Use the proper define for an error in RadosFsPriv::addPool
Rename RadosFsPriv's getPool to getDataPool
Add the getMetadataPool method to RadosFs

To do this, a generic getPool method was also added and used
in both getDataPool and getMetadataPool.
Add a getMetadataPoolPrefix method to RadosFs
Add a removeMetadataPool method to RadosFs
Add a metadataPoolFromPrefix method to RadosFs
Add a metadataPools method to RadosFs
test: Give a more specific name to the test pool

So it has less chances of clashing with existing pools.
test: Create a metadata pool for the tests to use
test: Update the Pools test to cover the metadata pool ops
Make stat check both data and metadata pools

Also introduces a new RadosFsPriv::stat to be used in other
methods since this already gives the right pool and the real
name of the object.