Switch to elasticsearch 7.x and build lma-build-prep early

There have been frequent 404 errors attempting to access the
artifacts.elastic.co archive for 5.x.

Change-Id: I04529e8d5584e006c090e790e9903592609343ee

snapcraft.yaml

@@ -646,6 +646,8 @@ parts:
   # Allows us to fetch things such as updated libvirt.
   uca-sources:
     plugin: nil
+    after:
+      - lma-build-prep
     build-packages:
       - ubuntu-cloud-keyring
       - software-properties-common
@@ -1536,7 +1538,7 @@ parts:
   filebeat:
     plugin: dump
     source: ./snap-wrappers/filebeat
-    after: [ lma-build-prep, qemu, libvirt ]
+    after: [ lma-build-prep ]
     stage-packages: [ filebeat ]
     organize:
       filebeat: bin/filebeat
@@ -1556,7 +1558,7 @@ parts:
       telegraf: bin/telegraf
     # we use autotools plugin here because it brings git, make
     # otherwise we'd have to add respective packages
-    after: [ lma-build-prep, qemu, libvirt ]
+    after: [ lma-build-prep ]
     # See https://forum.snapcraft.io/t/patchelf-broke-my-binary/4928
     # and https://bugs.launchpad.net/snapcraft/+bug/1753995
     build-attributes: [no-patchelf]
@@ -1571,7 +1573,7 @@ parts:
       cat $SNAPCRAFT_PROJECT_DIR/filebeat.pgp.key | apt-key add -
       cat $SNAPCRAFT_PROJECT_DIR/telegraf.pgp.key | apt-key add -
       apt-get install apt-transport-https
-      echo 'deb https://artifacts.elastic.co/packages/5.x/apt stable main' > /etc/apt/sources.list.d/elastic-5.x.list
+      echo 'deb https://artifacts.elastic.co/packages/7.x/apt stable main' > /etc/apt/sources.list.d/elastic-7.x.list
       echo 'deb http://ppa.launchpad.net/telegraf-devs/ppa/ubuntu bionic main' > /etc/apt/sources.list.d/telegraf.x.list
       # this needs to be re-worked in order to be built in-place
       echo 'deb http://ppa.launchpad.net/nikolay.vinogradov/nrpe-root/ubuntu bionic main' > /etc/apt/sources.list.d/nrpe-root.list