[v2] nsswitch: handle missing actions properly

[Siddhesh Poyarekar]

On 12/11/20 7:28 AM, DJ Delorie via Libc-alpha wrote:
> 
> v2: syntax fixed, added testcases.
> 
> ------------------------------
> 
> Some internal functions need to know if a database has a nonzero
> list of actions; success getting the database does not guarantee
> that.  Add checks for such as needed.
> 
> Skip the ":" in each nsswitch.conf line so as not to add a dummy
> action libnss_:.so
> 
> See also https://bugzilla.redhat.com/show_bug.cgi?id=1906066
> 

LGTM.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>