remove confusing comma syntax in if statements

There is a obscure bit of valid C syntax where you can run a statement in
an if statement, then put a comma, then the actual test.  The result of the
part before the comma is then ignored by the if statement.

This is ugly and unreadable, so I removed it.
fix when key_exists() in sqlfs_proc_write would not return EBUSY when busy

The annoying comma syntax in the if statement hid this bug.