s4:torture: Initialize struct netr_LogonSamLogonEx

s4:torture: Initialize struct netr_LogonSamLogonEx

"Error: UNINIT (CWE-457):
samba-4.20.0rc2/source4/torture/rpc/schannel.c:49: var_decl: Declaring variable ""r"" without initializer.
samba-4.20.0rc2/source4/torture/rpc/schannel.c:152: uninit_use_in_call: Using uninitialized value ""r.in.validation_level"" when calling ""torture_comment"".
  150|   			""LogonSamLogonEx failed"");
  151|   	} else {
  152|-> 		torture_comment(tctx,
  153|   				""Skip auth_level[%u] Testing LogonSamLogonEx with name %s using %s and validation_level: %d\n"",
  154|   				auth_level, ninfo.identity_info.account_name.string, crypto_alg,"

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Alexander Bokovoy <ab@samba.org>