factotum: Fix an operator precedence bug in the secstore code

`==` is higher precedence than `&`. Parenthesize.

Change-Id: I2c7ee588fea0d8a66e1c8424f26630015388d61a
Signed-off-by: Dan Cross <cross@gajendra.net>
Reviewed-on: https://plan9port-review.googlesource.com/2860
Reviewed-by: Gleydson Soares <gsoares@gmail.com>

src/cmd/auth/factotum/secstore.c

diff --git a/src/cmd/auth/factotum/secstore.c b/src/cmd/auth/factotum/secstore.c
index 2babf4d..c17c3cf 100644
--- a/src/cmd/auth/factotum/secstore.c
+++ b/src/cmd/auth/factotum/secstore.c
@@ -181,7 +181,7 @@
 	uchar count[2], digest[SHA1dlen];
 	int len, nr;
 
-	if(read(ss->fd, count, 2) != 2 || count[0]&0x80 == 0){
+	if(read(ss->fd, count, 2) != 2 || (count[0]&0x80) == 0){
 		werrstr("!SC_read invalid count");
 		return -1;
 	}