Remove unnecessary equality check

Remove unnecessary equality check

Currently `if` statement includes an assignment (from a function return
value) and a equality check. The parenthesis are in the incorrect place,
currently the code clobbers the function return value because of this.

We can fix this by simplifying the `if` statement.

`if (foo != 0)`

can be more succinctly expressed as

`if (foo)`

Remove the equality check, add parenthesis to correct the statement.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Closes #6685
Close #6719