Use https with apt in our ubuntu image builds

Debian is already doing this and according to ubuntu package search
apt-transport-https is a transitional package at least as far back as
bionic. We leave xenial with http as it isn't clear if apt there
supports https.

Change-Id: I455568f1e261060aefe555e9f5b4ef0830b60157

nodepool/nb03.opendev.org.yaml

@@ -120,7 +120,7 @@ diskimages:
       - ubuntu-minimal
     release: bionic
     env-vars:
-      DIB_DISTRIBUTION_MIRROR: 'http://mirror.regionone.linaro-us.opendev.org/ubuntu-ports'
+      DIB_DISTRIBUTION_MIRROR: 'https://mirror.regionone.linaro-us.opendev.org/ubuntu-ports'
       DIB_DEBIAN_COMPONENTS: 'main,universe'
 
   - name: ubuntu-focal-arm64
@@ -129,7 +129,7 @@ diskimages:
       - ubuntu-minimal
     release: focal
     env-vars:
-      DIB_DISTRIBUTION_MIRROR: 'http://mirror.regionone.linaro-us.opendev.org/ubuntu-ports'
+      DIB_DISTRIBUTION_MIRROR: 'https://mirror.regionone.linaro-us.opendev.org/ubuntu-ports'
       DIB_DEBIAN_COMPONENTS: 'main,universe'
 
   - name: debian-bullseye-arm64

nodepool/nodepool.yaml

@@ -295,7 +295,7 @@ diskimages:
       - cache-devstack
     release: bionic
     env-vars:
-      DIB_DISTRIBUTION_MIRROR: 'http://mirror.dfw.rax.opendev.org/ubuntu'
+      DIB_DISTRIBUTION_MIRROR: 'https://mirror.dfw.rax.opendev.org/ubuntu'
       DIB_DEBIAN_COMPONENTS: 'main,universe'
 
   - name: ubuntu-focal
@@ -306,7 +306,7 @@ diskimages:
       - cache-devstack
     release: focal
     env-vars:
-      DIB_DISTRIBUTION_MIRROR: 'http://mirror.dfw.rax.opendev.org/ubuntu'
+      DIB_DISTRIBUTION_MIRROR: 'https://mirror.dfw.rax.opendev.org/ubuntu'
       DIB_DEBIAN_COMPONENTS: 'main,universe'
 
   - name: ubuntu-jammy
@@ -317,7 +317,7 @@ diskimages:
       - cache-devstack
     release: jammy
     env-vars:
-      DIB_DISTRIBUTION_MIRROR: 'http://mirror.dfw.rax.opendev.org/ubuntu'
+      DIB_DISTRIBUTION_MIRROR: 'https://mirror.dfw.rax.opendev.org/ubuntu'
       DIB_DEBIAN_COMPONENTS: 'main,universe'
 
   - name: ubuntu-xenial