edge channel doesn't use hostname set by pmbootstrap (not on stable channel)

Describe your issue

What's the expected behaviour?

Hostname from /etc/hostname gets used, like on v20.05.

What's the current behaviour?

Getting a weird "unknown..." hostname, e.g.:

unknown02baed15228c:~$ cat /etc/hostname 
pine64-pinephone

How to reproduce your issue?

Generate a new pmbootstrap image from master

What device are you using?

Found with pine64-pinephone.

On what postmarketOS version did you encounter the issue?

• edge (master branch)
• stable (v20.05 branch)

On what environment did you encounter the issue?

Phone environments

• Phosh
• Plasma Mobile
• Sxmo

Other

• No environment
• GNOME
• KDE Plasma
• Kodi
• MATE
• Shelli
• Sway
• Weston
• Xfce4
• fbkeyboard
• i3wm

How did you get postmarketOS image?

• from https://images.postmarketos.org
• I built it using pmbootstrap
• It was preinstalled on my device

What's the build date of the image? (in dd-mm-yyyy format)

2020-09-08