test: cleaning cache must not clean lockfiles

Use-cases as shown in below containerfile cleans cache between the
builds, in previous commits we have ensured that buildah lockfiles will
not be part of user's cache content hence following use-case must paas

```
FROM quay.io/centos/centos:7

ARG WIPE_CACHE

RUN --mount=type=cache,target=/cache1,sharing=locked \
    --mount=type=cache,target=/cache2 \
    set -ex; \
    ls -l /cache1; \
    if [[ -v WIPE_CACHE ]]; then \
      >&2 echo "Wiping cache"; \
      find /cache1 -mindepth 1 -delete; \
    fi; \
    echo "foo" > /cache1/foo.txt; \
    ls -l /cache1; \
    chmod --recursive g=u /cache1; \
    : ;

RUN --mount=type=cache,target=/cache1,sharing=locked \
    >&2 echo "Never get here"
```

Closes: containers#4342

Signed-off-by: Aditya R <arajan@redhat.com>

tests/bud.bats

@@ -25,6 +25,14 @@ load helpers
   expect_output --substring "options use-vc"
 }
 
+#Verify https://github.com/containers/buildah/issues/4342
+@test "buildkit-mount type=cache should not hang if cache is wiped in between" {
+  containerfile=$BUDFILES/cache-mount-locked/Containerfile
+  run_buildah build $WITH_POLICY_JSON -t source -f $containerfile $BUDFILES/cache-mount-locked
+  # build should be success and must contain `hello` from `file` in last step
+  expect_output --substring "hello"
+}
+
 # Test for https://github.com/containers/buildah/pull/4295
 @test "build test warning for preconfigured TARGETARCH, TARGETOS, TARGETPLATFORM or TARGETVARIANT" {
   _prefetch alpine

tests/bud/cache-mount-locked/Containerfile

@@ -0,0 +1,21 @@
+FROM quay.io/centos/centos:7
+
+ARG WIPE_CACHE
+
+COPY file .
+
+RUN --mount=type=cache,target=/cache1,sharing=locked \
+    --mount=type=cache,target=/cache2 \
+    set -ex; \
+    ls -l /cache1; \
+    if [[ -v WIPE_CACHE ]]; then \
+      >&2 echo "Wiping cache"; \
+      find /cache1 -mindepth 1 -delete; \
+    fi; \
+    echo "foo" > /cache1/foo.txt; \
+    ls -l /cache1; \
+    chmod --recursive g=u /cache1; \
+    : ;
+
+# Cache was wiped-out but lock should not hang here: https://github.com/containers/buildah/issues/4342
+RUN --mount=type=cache,target=/cache1,sharing=locked cat file

tests/bud/cache-mount-locked/file

@@ -0,0 +1 @@
+hello