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.

test/t-09-loop/run.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 set -e
-. $(dirname ${0})/../util/lib.sh
+. "$(dirname "$0")/../util/lib.sh"
 
 init
 check_hostaliases
@@ -45,8 +45,8 @@ run_msmtp aliasB@srv-B < content
 # Get some of the debugging pages, for troubleshooting, and to make sure they
 # work reasonably well.
 function fexp_gt10() {
-	fexp $1 -save $2 && \
-		[ $( cat $2 | wc -l ) -gt 10 ]
+	fexp "$1" -save "$2" && \
+		[ "$( wc -l < "$2" )" -gt 10 ]
 }
 
 fexp_gt10 http://localhost:1099/ .data-A/dbg-root \