Update zpush.sh to version 2.7.4

[matidau]

Updating to latest release, bugfixes no new features.

Release: https://github.com/Z-Hub/Z-Push/releases/tag/2.7.4

Diff between 2.7.3 and 2.7.4: Z-Hub/Z-Push@2.7.3...2.7.4

[matidau]

Tested for the last week on my box, working like a charm.

[jvolkenant]

I've also been running this for the last month; working great. Thanks @matidau

[JoshData]

Thanks!