When setting process Smack label, fix labels of socket file descriptors

When setting process Smack label, fix labels of socket file descriptors

File descriptors for sockets get Smack labels when sockets are created.
But if Smack labels is changed for a process with open socket descriptors,
those descriptors keep the old Smack label. This should not happen during
application launch, because launched application could be identified as
a non-app user process.
To avoid this, all open file descriptors which happen to be sockets will
be relabeled inside security_manager_set_process_label_* functions.

Change-Id: I209a7a15edef7a2c20a9a4a00806a5d3876fb9e0
Signed-off-by: Rafal Krypa <r.krypa@samsung.com>