Skip apt hooks outside a running system

Port 4c9b44b0 from master, adapted to the stable layout.

userspace/usr/comma/apt_setup.sh

@@ -1,5 +1,10 @@
 #!/bin/bash -e
 
+# Skip unless this is a booted systemd system.
+if [ ! -d /run/systemd/system ]; then
+  exit 0
+fi
+
 sudo mount -o rw,remount /
 sudo resize2fs $(findmnt -n -o SOURCE /) &>/dev/null || sudo resize2fs $(findmnt -n -o SOURCE /)
 sudo mount -o remount,size=1500M /var

userspace/usr/comma/apt_teardown.sh

@@ -1,3 +1,8 @@
 #!/bin/bash
 
+# Skip unless this is a booted systemd system.
+if [ ! -d /run/systemd/system ]; then
+  exit 0
+fi
+
 sudo mount -o ro,remount / || true