Declare some configfs functions as static

Signed-off-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>
Add a SIGUSR1 handler for debugging purposes

Sending the SIGUSR1 signal to target-isns now invokes configfs_show()
to print the configfs hierarchy seen by target-isns in the logs.

Signed-off-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>
Fix target portal group not being created

Signed-off-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>
In TPG, rename 'id' to 'tag' and add tpg_find_by_tag()

Signed-off-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>
Add some logs around inotify

Signed-off-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>
Handle inotify events inside a TPG

Add inotify hooks for the TPG "enable" file and for the portal
creation / deletion.

Signed-off-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>