test-install: Fix shellcheck warnings.

In tools/test-install/destroy-all line 31:
  | while read c
          ^-- SC2162: read without -r will mangle backslashes.

In tools/test-install/install line 57:
    installer_dir="$(readlink -f $INSTALLER)"
                                 ^-- SC2086: Double quote to prevent globbing and word splitting.

In tools/test-install/lxc-wait line 30:
for i in {1..60}; do
^-- SC2034: i appears unused. Verify use (or export if used externally).

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

tools/test-install/destroy-all

@@ -28,7 +28,7 @@ fi
 
 lxc-ls -f \
   | perl -lane '$_ = $F[0]; print if (/^zulip-install-/ && !/-base$/)' \
-  | while read c
+  | while read -r c
 do
     echo "$c"
     lxc-stop -n "$c"

tools/test-install/install

@@ -54,7 +54,7 @@ EOF
 trap 'set +x; echo "$message"' EXIT
 
 if [ -d "$INSTALLER" ]; then
-    installer_dir="$(readlink -f $INSTALLER)"
+    installer_dir="$(readlink -f "$INSTALLER")"
 else
     installer_dir="$(mktemp -d --tmpdir zulip-server-XXXXX)"
     tar -xf "$INSTALLER" -C "$installer_dir" --transform='s,^[^/]*,zulip-server,'

tools/test-install/lxc-wait

@@ -27,7 +27,7 @@ if [ "$EUID" -ne 0 ]; then
 fi
 
 # We poll.
-for i in {1..60}; do
+for _ in {1..60}; do
     echo "lxc-wait: $CONTAINER_NAME: polling for boot..." >&2
     runlevel="$(lxc-attach -n "$CONTAINER_NAME" -- runlevel 2>/dev/null)" \
         || { sleep 1; continue; }