Documentation: nfs: fault_injection: convert to ReST

Convert fault_injection.txt to ReST and move it to admin-guide.
Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Link: https://lore.kernel.org/r/f7b0cf8fb1159a668f75ce82a581e7590568c2b8.1578697871.git.dwlsalmeida@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/nfs/fault_injection.txt → Documentation/admin-guide/nfs/fault_injection.rst

+===================
+NFS Fault Injection
+===================
 
-Fault Injection
-===============
 Fault injection is a method for forcing errors that may not normally occur, or
 may be difficult to reproduce.  Forcing these errors in a controlled environment
 can help the developer find and fix bugs before their code is shipped in a

Documentation/admin-guide/nfs/index.rst

@@ -12,3 +12,4 @@ NFS
     nfs-idmapper
     pnfs-block-server
     pnfs-scsi-server
+    fault_injection