install.sh: initial support for sle-micro (#4331)

Support invoking install.sh on SLE Micro with or without SELinux
enabled. Same deal for SLES.

Additionally, easy-to-invoke assertions, via Vagrant, that the local
install.sh works correctly:
- tests/install/centos-7 (stand-in for rhel 7)
- tests/install/centos-8 (stand-in for rhel 8)
- tests/install/opensuse-leap (stand-in for sles)
- tests/install/opensuse-microos (stand-in for sle-micro)
- tests/install/ubuntu-focal

Addresses #3188
Addresses #3917

Signed-off-by: Jacob Blain Christen <jacob@rancher.com>

.github/workflows/unitcoverage.yaml

@@ -1,11 +1,15 @@
 name: Unit Test Coverage
-on: 
+on:
   push:
-    paths-ignore: 
+    paths-ignore:
       - "**.md"
+      - "install.sh"
+      - "tests/install"
   pull_request:
     paths-ignore:
       - "**.md"
+      - "install.sh"
+      - "tests/install"
   workflow_dispatch: {}
 jobs:
   test: