tools/xenstored: Remove redundant check in socket_can_process()

tools/xenstored: Remove redundant check in socket_can_process()

Commit 3adfb50315d9 ("tools/xenstored: Introduce a wrapper for
conn->funcs->can_{read, write}") consolidated the check
!conn->is_ignored in two new wrappers.

This means the check in socket_can_process() is now redundant. In
fact it should have been removed in orignal commit (as it was done
for the domain helpers).

Reported-by: Raphael Ning <raphning@amazon.com
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Juergen Gross <jgross@suse.com>