Few more shellcheck warnings fixes/ignores

misc/qubes-serial-login

@@ -1,6 +1,6 @@
 #!/bin/sh
 if /bin/ls -l /proc/self/fd/0 | grep -q /dev/hvc0 ; then
-	exec su - $2
+	exec su - "$2"
 	exit
 else
 	exec /bin/login "$@"

misc/upgrades-installed-check

@@ -9,6 +9,7 @@
 
 if [ -e /etc/system-release ]; then
    ## Fedora
+   # shellcheck disable=SC2034
    yum_output="$(yum -q check-update 2>&1)"
    exit_code="$?"
    [ "$exit_code" -eq 100 ] && echo "false" && exit 0
@@ -17,6 +18,7 @@ elif [ -e /etc/debian_version ]; then
    ## Debian
    set -e
    set -o pipefail
+   # shellcheck disable=SC2034
    apt_get_update_output="$(apt-get -q update 2>&1)"
    apt_get_upgrade_output="$(LANG="C" apt-get -s upgrade 2>&1)"
    exit_code="$?"

qrexec/qubes-rpc-multiplexer

@@ -37,10 +37,12 @@ for CFG_FILE in $LOCAL_QUBES_RPC/"$1" $QUBES_RPC/"$1" \
 done
 
 if [ -x "$CFG_FILE" ] ; then
+    # shellcheck disable=SC2086
 	exec "$CFG_FILE" ${QREXEC_SERVICE_ARGUMENT}
 	echo "$0: failed to execute handler for" "$1" >&2
 	exit 1
 else
+    # shellcheck disable=SC2086
 	exec /bin/sh -- "$CFG_FILE" ${QREXEC_SERVICE_ARGUMENT}
 	echo "$0: failed to execute handler for" "$1" >&2
 	exit 1