Add basic tests for all base combinations of session recording
configuration options.

Add exporting of original user shell (as returned by NSS) as an
environment variable for use by tlog-rec, when session recording is
enabled for the user. This lets tlog-rec start the actual user shell,
after tlog-rec is started in its place.

Substitute the configured session recording shell when unconditional
session recording is enabled (scope = all), or when selective session
recording is enabled (scope = some), and the user has the
sessionRecording attribute set to true.

After entires are retrieved by cache_req for user info requests (except
initgr), overlay them with sessionRecording attribute retrieved from an
initgr request made additionally for each entry.

Do not do additional initgr requests with selective session recording
enabled, if we don't have any group names to match against in session
recording configuration. Only do user name matches instead.

Add sessionRecording attribute to user entries on initgr request in data
provider, specifying if the user name or groups match the ones with
session recording enabled.

Add loading and storing the override_space configuration option to data
provider. That will be needed for formatting output user and group names
for matching against session recording configuration.

Add a macro for sessionRecording attribute to sysdb.h.
To be used for storing a boolean attribute signifying if session
recording is enabled for the user.

Add session recording configuration loading to the data provider
initialization. To be used for matching users and groups with session
recording enabled.

Add session recording configuration loading to the common responder
initialization. To be used for substituting the user shell when
session recording is enabled.