s3:winbind: Fix uninitialized validation_level variable

s3:winbind: Fix uninitialized validation_level variable

Found by oss-fuzz:

../../source3/winbindd/winbindd_pam.c:2879:7: error: variable 'validation_level' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
                 if (!(state->request->flags & WBFLAG_BIG_NTLMV2_BLOB) ||
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ../../source3/winbindd/winbindd_pam.c:3003:6: note: uninitialized use occurs here
             validation_level,
             ^~~~~~~~~~~~~~~~
 ../../source3/winbindd/winbindd_pam.c:2879:3: note: remove the 'if' if its condition is always false
                 if (!(state->request->flags & WBFLAG_BIG_NTLMV2_BLOB) ||
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ../../source3/winbindd/winbindd_pam.c:2879:7: error: variable 'validation_level' is used uninitialized whenever '||' condition is true [-Werror,-Wsometimes-uninitialized]
                 if (!(state->request->flags & WBFLAG_BIG_NTLMV2_BLOB) ||
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ../../source3/winbindd/winbindd_pam.c:3003:6: note: uninitialized use occurs here
             validation_level,
             ^~~~~~~~~~~~~~~~
 ../../source3/winbindd/winbindd_pam.c:2879:7: note: remove the '||' if its condition is always false
                 if (!(state->request->flags & WBFLAG_BIG_NTLMV2_BLOB) ||
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ../../source3/winbindd/winbindd_pam.c:2853:27: note: initialize the variable 'validation_level' to silence this warning
         uint16_t validation_level;
                                  ^
                                   = 0
 1 warning and 2 errors generated.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15044

Signed-off-by: Samuel Cabrero <scabrero@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Apr 12 18:54:50 UTC 2022 on sn-devel-184