Spurious solution for trig formula in Maxima

<div id="comment:0"></div>

Reported at [this SF bug](https://sourceforge.net/p/maxima/bugs/2773/), we have 

```
solve([sin(cos(x))/cos(x)==0],x) gives: 
[x == 1/2*pi]
```

Upstream: **Reported upstream. No feedback yet.**

Component: **calculus**

_Issue created by migration from https://trac.sagemath.org/ticket/16593_

