util: storage: Add fields for debug options for disk drivers

Some drive backends allow output of debugging information which can be
configured using properties of the image. Add fields to virStorageSource
which will allow configuring them.

src/util/virstoragefile.c

@@ -2061,6 +2061,8 @@ virStorageSourceCopy(const virStorageSource *src,
     ret->tlsFromConfig = src->tlsFromConfig;
     ret->tlsVerify = src->tlsVerify;
     ret->detected = src->detected;
+    ret->debugLevel = src->debugLevel;
+    ret->debug = src->debug;
 
     /* storage driver metadata are not copied */
     ret->drv = NULL;

src/util/virstoragefile.h

@@ -303,6 +303,9 @@ struct _virStorageSource {
     bool tlsVerify;
 
     bool detected; /* true if this entry was not provided by the user */
+
+    unsigned int debugLevel;
+    bool debug;
 };