Fix grains with '\n'

[dincamihai]

What does this PR do?

Fixes the grains that contain a trailing new line char.

bash-4.3# salt-call --local grains.items --out=json > /tmp/before.json
# apply fix here
bash-4.3# salt-call --local grains.items --out=json > /tmp/after.json
bash-4.3# diff /tmp/before.json /tmp/after.json
3c3
<         "biosversion": "A14\n",
---
>         "biosversion": "A14",
27,28c27,28
<         "serialnumber": "GLK3A32\n",
<         "pid": 536,
---
>         "serialnumber": "GLK3A32",
>         "pid": 553,
57c57
<         "uuid": "2c3c1621-011x-5910-2163-b5a03f3c3834\n",
---
>         "uuid": "2c3c1621-011x-5910-2163-b5a03f3c3834",
227,228c227,228
<         "biosreleasedate": "09/14/2015\n",
<         "manufacturer": "Dell Inc.\n",
---
>         "biosreleasedate": "09/14/2015",
>         "manufacturer": "Dell Inc.",
249c249
<         "productname": "OptiPlex 9020\n",
---
>         "productname": "OptiPlex 9020",

Tests written?

No

Commits signed with GPG?

No