tests/kola: Move to tests/kolainst

Follow the precedent set in https://github.com/coreos/rpm-ostree/pull/2106
and rename the directory, to more clearly move away from the
"uninstalled" test model.  Prep for Rust-based tests.

.cci.jenkinsfile

@@ -76,9 +76,8 @@ parallel fcos: {
         rmdir insttree
         coreos-assembler fetch
         coreos-assembler build
-        # Install the tests, then be sure they're not run again
-        make -C tests/kola install
-        rm tests/kola -rf
+        # Install the tests
+        make -C tests/kolainst install
       """)
     }
     fcosKola(cosaDir: "${env.WORKSPACE}")