tests/int: fix teardown in mounts_sshfs.bats

Function teardown assumes that every test case will call
setup_sshfs. Currently, this assumption is true, but once
a test case that won't call setup_sshfs is added (say because
it has some extra "requires" or "skip"), it will break bats,
so any bats invocation involving such a test case will end up
hanging after the last test case is run.

The reason is, we have set -u in helpers.bash to help catching the use
of undefined variables. In the above scenario, such a variable is DIR,
which is referenced in teardown but is only defined after a call to
setup_sshfs. As a result, bash that is running the teardown function
will exit upon seeing the first $DIR, and thus teardown_bundle won't be
run. This, in turn, results in a stale recvtty process, which inherits
bats' fd 3. Until that fd is closed, bats waits for test logs.

Long story short, the fix is to
 - check if DIR is set before referencing it;
 - unset it after unmount.

PS it is still not clear why there is no diagnostics about the failed
teardown.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

tests/integration/mounts_sshfs.bats

@@ -8,9 +8,12 @@ function setup() {
 }
 
 function teardown() {
-	# Some distros do not have fusermount installed
-	# as a dependency of fuse-sshfs, and good ol' umount works.
-	fusermount -u "$DIR" || umount "$DIR"
+	if [ -v DIR ]; then
+		# Some distros do not have fusermount installed
+		# as a dependency of fuse-sshfs, and good ol' umount works.
+		fusermount -u "$DIR" || umount "$DIR"
+		unset DIR
+	fi
 
 	teardown_bundle
 }