APPLIED[Unstable]: [PATCH][SRU][E/Unstable] UBUNTU: [Debian] Fix warnings when checking for modules signatures

[Seth Forshee]

On Mon, Nov 25, 2019 at 08:34:51AM -0600, Seth Forshee wrote:
> BugLink: https://bugs.launchpad.net/bugs/1853843
> 
> When detecting module signatures, the current approach causes
> this warning for modules lacking a signature:
> 
>  /bin/bash: line 5: warning: command substitution: ignored null byte in input
> 
> My original approach used read, which works well, but for unknown
> reasons causes an error from bash when by itself as the first
> line in the if clause. Putting it in a no-op while loop prevents
> the error, but it has the advantage of working without flooding
> the build logs with warnings.
> 
> Signed-off-by: Seth Forshee <seth.forshee at canonical.com>

Applied to unstable/master.