signals: sys_ssetmask() uses uninitialized newmask

Commit 77097ae503b1 ("most of set_current_blocked() callers want
SIGKILL/SIGSTOP removed from set") removed the initialization of newmask
by accident, causing ltp to complain like this:

  ssetmask01    1  TFAIL  :  sgetmask() failed: TEST_ERRNO=???(0): Success

Restore the proper initialization.

Reported-and-tested-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@kernel.org	# v3.5+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/signal.c b/kernel/signal.c
index 7aaa51d..9692499 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3286,6 +3286,7 @@
 	int old = current->blocked.sig[0];
 	sigset_t newset;
 
+	siginitset(&newset, newmask);
 	set_current_blocked(&newset);
 
 	return old;