Description of problem:

For the NFS exports identified with the fsid=0 option which means it's the root of all exported filesystem, previously (rhel-7.3) we can only mount it with command "mount -t nfs4 server:/ /mnt/home", while command "mount -t nfs4 server:/home /mnt/home" gets failed.  The difference being "server:/home" and "server:/".

But now with the latest nfs-utils, command "mount -t nfs4 server:/home /mnt/home" successes and it actually mounts with NFS version 3.


Version-Release number of selected component (if applicable):
Start from nfs-utils-1.3.0-0.35.el7 until latest version (1.3.0-0.41.el7)
(Haven't test version 1.3.0-0.34.el7 as cannot download it for now)

How reproducible:
100% easily

Steps to Reproduce:
1. echo "/home *(rw,fsid=0,sync)" > /etc/exports
                    ^^^^^^
2. systemctl restart nfs
3. mount -t nfs4 127.0.0.1:/home /mnt/test
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ should be failed

Actual results:
[root@hp-dl360g9-14 ~]# cat /etc/exports
/home *(rw,fsid=0,sync)
[root@hp-dl360g9-14 ~]# systemctl restart nfs
[root@hp-dl360g9-14 ~]# exportfs -v
/home         	<world>(rw,sync,wdelay,hide,no_subtree_check,fsid=0,sec=sys,secure,root_squash,no_all_squash)
[root@hp-dl360g9-14 ~]# mount -o vers=4 127.0.0.1:/home/ /mnt/mnt_test/
[root@hp-dl360g9-14 ~]# echo $?
0
[root@hp-dl360g9-14 ~]# nfsstat -m
/mnt/mnt_test from 127.0.0.1:/home/
 Flags:	rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=127.0.0.1,mountvers=3,mountport=20048,mountproto=udp,local_lock=none,addr=127.0.0.1

[root@hp-dl360g9-14 ~]# umount /mnt/mnt_test/
[root@hp-dl360g9-14 ~]# mount -t nfs4 127.0.0.1:/home/ /mnt/mnt_test/ -vvv
mount.nfs4: timeout set for Wed May  3 22:54:56 2017
mount.nfs4: trying text-based options 'vers=4.1,addr=127.0.0.1,clientaddr=127.0.0.1'
mount.nfs4: mount(2): No such file or directory
mount.nfs4: trying text-based options 'addr=127.0.0.1'
mount.nfs4: prog 100003, trying vers=3, prot=6
mount.nfs4: trying 127.0.0.1 prog 100003 vers 3 prot TCP port 2049
mount.nfs4: prog 100005, trying vers=3, prot=17
mount.nfs4: trying 127.0.0.1 prog 100005 vers 3 prot UDP port 20048
[root@hp-dl360g9-14 ~]# umount /mnt/mnt_test/
[root@hp-dl360g9-14 ~]#
[root@hp-dl360g9-14 ~]# mount -o vers=4 127.0.0.1:/home/ /mnt/mnt_test/ -vvv
mount.nfs: timeout set for Wed May  3 22:58:06 2017
mount.nfs: trying text-based options 'vers=4,addr=127.0.0.1,clientaddr=127.0.0.1'
mount.nfs: mount(2): No such file or directory
mount.nfs: trying text-based options 'addr=127.0.0.1'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 127.0.0.1 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 127.0.0.1 prog 100005 vers 3 prot UDP port 20048
[root@hp-dl360g9-14 ~]# umount /mnt/mnt_test/
[root@hp-dl360g9-14 ~]# rpm -q nfs-utils
nfs-utils-1.3.0-0.35.el7.x86_64
[root@hp-dl360g9-14 ~]# 


Expected results:
### downgrade nfs-utils to 1.3.0-0.33.el7 ###
[root@hp-dl360g9-14 ~]# rpm -q nfs-utils
nfs-utils-1.3.0-0.33.el7.x86_64
[root@hp-dl360g9-14 ~]# exportfs -v
/home         	<world>(rw,wdelay,root_squash,no_subtree_check,fsid=0,sec=sys,rw,secure,root_squash,no_all_squash)
[root@hp-dl360g9-14 ~]# mount -t nfs4 127.0.0.1:/home/ /mnt/mnt_test/ -vvv
mount.nfs4: timeout set for Wed May  3 22:57:04 2017
mount.nfs4: trying text-based options 'addr=127.0.0.1,clientaddr=127.0.0.1'
mount.nfs4: mount(2): No such file or directory
mount.nfs4: mounting 127.0.0.1:/home/ failed, reason given by server: No such file or directory
[root@hp-dl360g9-14 ~]# mount -o vers=4 127.0.0.1:/home/ /mnt/mnt_test/ -vvv
mount.nfs: timeout set for Wed May  3 22:57:24 2017
mount.nfs: trying text-based options 'vers=4,addr=127.0.0.1,clientaddr=127.0.0.1'
mount.nfs: mount(2): No such file or directory
mount.nfs: mounting 127.0.0.1:/home/ failed, reason given by server: No such file or directory
[root@hp-dl360g9-14 ~]# 


Additional info:
Maybe introduced by Bug 1375259 (same as Bug 1404617)