Improve bash quoting, and other similar best practices

This patch updates the shell scripts with some of the common best
practices, which should make them more resilient to unusual failures and
unexpected environments (in particular, directories with spaces).

Most of these were identified by shellcheck.

cmd/chasquid-util/test.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 set -e
-. $(dirname ${0})/../../test/util/lib.sh
+. "$(dirname "$0")/../../test/util/lib.sh"
 
 init
 

cmd/dovecot-auth-cli/test.sh

@@ -1,13 +1,14 @@
 #!/bin/bash
 
 set -e
-. $(dirname ${0})/../../test/util/lib.sh
+. "$(dirname "$0")/../../test/util/lib.sh"
 
 init
 
 # Build the binary once, so we can use it and launch it in chamuyero scripts.
 # Otherwise, we not only spend time rebuilding it over and over, but also "go
 # run" masks the exit code, which is something we care about.
+# shellcheck disable=SC2086
 if [ "${COVER_DIR}" != "" ]; then
 	go test -covermode=count -coverpkg=../../... -c \
 		$GOFLAGS -tags="coveragebin $GOTAGS"
@@ -22,9 +23,9 @@ if ! ./dovecot-auth-cli lalala 2>&1 | grep -q "invalid arguments"; then
 fi
 
 for i in *.cmy; do
-	if ! chamuyero $i > $i.log 2>&1 ; then
+	if ! chamuyero "$i" > "$i.log" 2>&1 ; then
 		echo "# Test $i failed, log follows"
-		cat $i.log
+		cat "$i.log"
 		exit 1
 	fi
 done

cmd/mda-lmtp/test.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 set -e
-. $(dirname ${0})/../../test/util/lib.sh
+. "$(dirname "$0")/../../test/util/lib.sh"
 
 init
 
@@ -11,9 +11,9 @@ init
 go build
 
 for i in *.cmy; do
-	if ! chamuyero $i > $i.log 2>&1 ; then
+	if ! chamuyero "$i" > "$i.log" 2>&1 ; then
 		echo "# Test $i failed, log follows"
-		cat $i.log
+		cat "$i.log"
 		exit 1
 	fi
 done