As noted by @buxm, previous fix didn't work for all versions of DSM 6.
The better fix appears to be simply not outputting the "as_default"
parameter unless we are doing something with the default certificate.
For some DSM installs, it appears that setting the "default" flag to the
string "false" actually sets it to true. This causes Synology to set
the last updated certificate to be the default certificate. Using an
empty string appears to still be accepted as a false-y value for DSMs
where this isn't happening and corrects the behavior in the cases that
it was.
Credit to @Run-King for identifying the fix and @buxm for reporting.
On systems that /bin/sh is served by shells other than bash, or
shells that don't implement the same syntax as the bash printf builtin,
printf -- fails to produce the output necessary for standalone operation.
The test case for this was SmartOS, which uses ksh93 as its /bin/sh.
This change uses the more generic method of passing a format parameter
of a single string, and then the argument to replace it with.
When using vault_cli with a kv2 path, it isn't working. I have the following error:
```
WARNING! The following warnings were returned from Vault:
* Invalid path for a versioned K/V secrets engine. See the API docs for the
appropriate API endpoints to use. If using the Vault CLI, use 'vault kv put'
for this operation.
```
The new way to write data is to use `vault kv put`, it is compatible with kv1 and kv2.
Ref: https://www.vaultproject.io/docs/commands#reading-and-writing-data
```
The original version of K/V used the common read and write operations. A more advanced K/V Version 2 engine was released in Vault 0.10 and introduced the kv get and kv put commands.
```
