smbstatus: add opens to files in json output

smbstatus: add opens to files in json output

At the moment, there is only information about the open files.
Adds a list of its opens for each file. An open is represented as
a dictionary. Contains only the basic information (pid, uid and
time) about the open.

Signed-off-by: Jule Anger <janger@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>