Merge pull request #3557 from ycdzj/fix/alpine_bash

fix(cidata): do not overwrite bash in alpine vm

Author: AkihiroSuda

pkg/cidata/cidata.TEMPLATE.d/boot/01-alpine-ash-as-bash.sh

@@ -7,6 +7,9 @@
 # cloud-init scripts can use `#!/bin/bash` and `set -o pipefail`.
 test -f /etc/alpine-release || exit 0
 
+# If bash already exists, do nothing.
+test -x /bin/bash && exit 0
+
 # Redirect bash to ash (built with CONFIG_ASH_BASH_COMPAT) and hope for the best :)
 # It does support `set -o pipefail`, but not `[[`.
 # /bin/bash can't be a symlink because /bin/ash is a symlink to /bin/busybox