Fix command of nfs test mount missing mountpoint argument

The command to mount the nfs shares to the filesystem is missing the directory where the nfs share should be mounted to.

Ref: Manpage MOUNT(8)
mount [-t <fstype>] device mountpoint

Author: FuzzyDoge

source/installguide/management-server/_nfs.rst

@@ -253,8 +253,8 @@ operating system version.
       .. parsed-literal::
 
          mkdir /primary
-         mount -t nfs <management-server-name>:/export/primary
+         mount -t nfs <management-server-name>:/export/primary /primary
          umount /primary
          mkdir /secondary
-         mount -t nfs <management-server-name>:/export/secondary
+         mount -t nfs <management-server-name>:/export/secondary /secondary
          umount /secondary