fix: Allow clamd to start normally when a whitelist is present.

The given functionality was introduced in the [following commit](e4fe665)
and after taking a look at the [cli_cvdverify](https://github.com/Cisco-Talos/clamav/blob/e4fe6654c1618bacf3bff9ed64c52615c8c53a97/libclamav/cvd.c#L530) function I believe it is meant to verify only CVDs.

That is, it throws an error when encountering a clear text (whitelist, `ign`,`.ign2`) file.
I mimicked the way the allowed extensions in the Database folder were handled, and excluded the 2 clear text extensions mentioned above.
This has locally allowed for the normal execution of `clamd`.

libclamav/cvd.c

@@ -851,7 +851,7 @@ cl_error_t cl_cvdgetage(const char *path, time_t *age_seconds)
         if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
             continue;
 
-        if (!CLI_DBEXT(dent->d_name))
+        if (!CLI_DBEXT(dent->d_name) || CLI_DBEXT_IGNORE(dent->d_name))
             continue;
 
         if (ends_with_sep)

libclamav/readdb.h

@@ -81,6 +81,10 @@ struct cli_matcher;
         cli_strbcasestr(ext, ".ign") ||  \
         cli_strbcasestr(ext, ".ign2") || \
         cli_strbcasestr(ext, ".imp"))
+#define CLI_DBEXT_IGNORE(ext)           \
+    (                                   \
+        cli_strbcasestr(ext, ".ign") ||  \
+        cli_strbcasestr(ext, ".ign2"))
 #else
 #define CLI_DBEXT(ext)                   \
     (                                    \
@@ -120,6 +124,10 @@ struct cli_matcher;
         cli_strbcasestr(ext, ".ign") ||  \
         cli_strbcasestr(ext, ".ign2") || \
         cli_strbcasestr(ext, ".imp"))
+#define CLI_DBEXT_IGNORE(ext)           \
+    (                                   \
+        cli_strbcasestr(ext, ".ign") ||  \
+        cli_strbcasestr(ext, ".ign2"))
 #endif
 
 char *cli_virname(const char *virname, unsigned int official);