updating clamav defintions test to include possbility of .cld files

ClamAV will sometimes include files with a .cld extension, rather than the more common .cvd definitions. ClamAV documentation:

2. FreshClam checks the ClamAV virus database directory (indicated by the DatabaseDirectory value in the freshclam.conf that FreshClam uses) for existing instances of main.cvd, daily.cvd, or bytecode.cvd. For main and daily, if the CVD can’t be found it also looks for main.cld and daily.cld. These CLD files are uncompressed and unsigned versions of the CVD that have had CDIFFs applied.

This update accounts for that when we check if the files are present.