huxtable hhlines don't work in beamer

[hughjonesd]

Split off from the other beamer bug.

See https://tex.stackexchange.com/questions/404872/are-beamer-hhline-and-tablexcolor-incompatible#comment1009168_404903

MWE:

---
title: "Untitled"
author: "David Hugh-Jones"
date: "27/10/2017"
output: 
  beamer_presentation:
    keep_tex: true
header-includes:
  - \usepackage{array}
  - \usepackage{caption}
  - \usepackage{graphicx}
  - \usepackage{siunitx}
  - \usepackage{ulem}
  - \usepackage{colortbl}
  - \usepackage{multirow}
  - \usepackage{hhline}
  - \usepackage{calc}
  - \usepackage{tabularx}
  - \usepackage{threeparttable}
  - \usepackage{wrapfig}
  - \usepackage{adjustbox}
---

# A slide {.fragile}

```{r table1hux, echo = FALSE}
library(huxtable)
set_all_borders(jams)
```

[hughjonesd]

See also josephwright/beamer#434.

[hughjonesd]

@ramattheis