tools/cgsnapshot: Fix Coverity uninitialized variable warning

tools/cgsnapshot: Fix Coverity uninitialized variable warning

Coverity reported the following uninitialized variable warning:

CID 465887: (#1 of 1): Uninitialized scalar variable (UNINIT)
32. uninit_use_in_call: Using uninitialized value *wl_file when calling load_list.

Fix the issue by initializing the char[] wl_file with '\0', and also
initialize dl_file similarly as a best practice.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>