change case sensitive string match to case insensitive

change case sensitive string match to case insensitive

With the rewrite from C to Rust the search string match was changed to
be case sensitive by accident. Fix this by comparing the lowercase values
of both the input and the search string.

Signed-off-by: Mira Limbeck <m.limbeck@proxmox.com>
Reviewed-By: Stoiko Ivanov <s.ivanov@proxmox.com>
Tested-By: Stoiko Ivanov <s.ivanov@proxmox.com>