move helper gating script to tests dir

Sometimes changes to the helper script for the gating plan are needed
without a ticket. Since this is a shell script, it is not exempt from
dist-git policy that requires a ticket for any non-test change. The
gating plan itself is a fmf file which is exempt, so only this used to
be a problem in the past.

Because of the STI test format, the whole tests folder is exempt too.
Moving the helper script there to avoid the need for tickets.

plan-gating.fmf

@@ -0,0 +1,32 @@
+summary: PCS gating test plan
+description: Runs upstream tier0, tier1 and smoke tests
+
+discover:
+    dist-git-source: true
+    dist-git-install-builddeps: true
+    how: shell
+    tests:
+        - name: tier0
+          test: |
+              ./tests/prepare-tests.sh
+              $TMT_SOURCE_DIR/pcs-*/pcs_test/suite --tier0 -v --vanilla --installed
+          duration: 10m
+          tier: 0
+          tag: fast
+        - name: tier1
+          test: |
+              ./tests/prepare-tests.sh
+              $TMT_SOURCE_DIR/pcs-*/pcs_test/suite --tier1 -v --vanilla --installed
+          duration: 2h
+          tier: 1
+        - name: smoke
+          test: |
+              systemctl start pcsd
+              ./tests/prepare-tests.sh
+              $TMT_SOURCE_DIR/pcs-*/pcs_test/smoke.sh
+          duration: 10m
+          tier: smoke
+          tag: fast
+
+execute:
+    how: tmt

tests/prepare-tests.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+set -eo xtrace
+cd $TMT_SOURCE_DIR
+# Use stamp file to abort if this script already ran
+if [ -e tests-prepared-stamp ]; then exit 0; fi
+# RPM 4.20 changed the builddir structure - unpacked sources go to *-build but
+# tmt copies them back to pcs-*, so the pcs-*-build folder is empty
+# Remove pcs-web-ui, pcs-*-build for "cd pcs-*" to have exactly one match
+rm -rf pcs-web-ui-* pcs-*-build
+cd pcs-*/
+# Run autotools, use bundled dependencies from the system
+export PYTHONPATH=/usr/lib/pcs/pcs_bundled/packages/
+export GEM_HOME=/usr/lib/pcsd/vendor/bundle/
+# We need to use cd pcs-* because when pcs-web-ui starts using autotools, running
+# autogen and configure with expanded TMT_SOURCE_DIR will match that too
+./autogen.sh
+./configure --enable-local-build --enable-use-local-cache-only \
+  --enable-individual-bundling --enable-webui --with-pcs-lib-dir=/usr/lib
+# Remove pcs sources to make sure tests are not using any of those files
+rm -rf pcs
+touch ../tests-prepared-stamp