knfsd: fix broken length check in nfs4idmap.c
knfsd: fix broken length check in nfs4idmap.c

Obviously at some point we thought "error" represented the length when
positive.  This appears to be a long-standing typo.

Thanks to Prasad Potluri <be3496867040cc0df9c36630e6f8790332466b6a@us.ibm.com> for finding the problem and
proposing an earlier version of this patch.

Cc: Steve French <2e55bd25036f9445fc868a69738648d24569fa51@us.ibm.com>
Cc: Prasad V Potluri <be3496867040cc0df9c36630e6f8790332466b6a@us.ibm.com>
Signed-off-by: J. Bruce Fields <51738506c1b2ccb0761f23bdc612c93babf738ea@citi.umich.edu>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas