tcpdump does not support NFSv4 and prints out wrong NFS data which
always be "getattr" for NFSv4, because both NFSv4 COMPOUND procedure
and NFSv2/3 GETATTR procedure are the same value '1'.

This is a minimum support for NFSv4, which detects NFSv4 and can print
out NULL procedure or COMPOUND procedure at least.

Log of current no-NFSv4 support:
  NFS4_OK case
    18:03:38.718964 IP client.815 > server.nfs: Flags [P.], seq 192:312, ack 177, win 22430, options [nop,nop,TS val 2190058497 ecr 3789310763], length 120: NFS request xid 1660218411 116 getattr fh 0,1/53
    18:03:38.719279 IP server.nfs > client.815: Flags [P.], seq 177:261, ack 312, win 3333, options [nop,nop,TS val 3789310764 ecr 2190058497], length 84: NFS reply xid 1660218411 reply ok 80 getattr NON 1 ids 0/159 sz -719751424
  NFS4ERR_NOENT case
    18:03:44.707900 IP client.815 > server.nfs: Flags [P.], seq 312:512, ack 261, win 22430, options [nop,nop,TS val 2190064486 ecr 3789310864], length 200: NFS request xid 1676995627 196 getattr fh 0,1/53
    18:03:44.708575 IP server.nfs > client.815: Flags [P.], seq 261:361, ack 512, win 3333, options [nop,nop,TS val 3789316753 ecr 2190064486], length 100: NFS reply xid 1676995627 reply ok 96 getattr ERROR: No such file or directory

Log of this minimum NFSv4 support:
  NFS4_OK case
    18:06:18.975026 IP client.815 > server.nfs: Flags [P.], seq 488:608, ack 549, win 22430, options [nop,nop,TS val 2190218753 ecr 3789464067], length 120: NFS request xid 1861545003 116 v4 compound
    18:06:18.975276 IP server.nfs > client.815: Flags [P.], seq 549:633, ack 608, win 3333, options [nop,nop,TS val 3789471020 ecr 2190218753], length 84: NFS reply xid 1861545003 reply ok 80 v4 compound
  NFS4ERR_NOENT case
    17:51:08.684565 IP client.815 > server.nfs: Flags [P.], seq 432:632, ack 345, win 22430, options [nop,nop,TS val 2189308462 ecr 3788560729], length 200: NFS request xid 888466475 196 v4 compound
    17:51:08.685081 IP server.nfs > client.815: Flags [P.], seq 345:445, ack 632, win 3333, options [nop,nop,TS val 3788560730 ecr 2189308462], length 100: NFS reply xid 888466475 reply ok 96 v4 compound ERROR: No such file or directory

Signed-off-by: Seiichi Ikarashi <s.ikarashi@fujitsu.com>

A test for NFSv4 support.

Signed-off-by: Seiichi Ikarashi <s.ikarashi@fujitsu.com>

Support NFSv4 errors, and update "nfs-v4" test case to include NFSv4 NULL procedure.

Add support for showing NFSv4 minor version and numops from the COMPOUND request.
Also fix some tab-indent bug in interp_reply().