SUNRPC: Display some debugging information as text rather than numbers

In rpc_show_tasks(), display the program name, version number, procedure
name and tk_action as human-readable variable-length text fields rather
than columnar numbers.

Doing the symbol lookup here helps in cases where we have actual
debugging output from a kernel log, but don't have access to the kernel
image or RPC module that generated the output.

Sample output:

 -pid- flgs status -client- --rqstp- -timeout ---ops--
  5608 0001    -11 eeb42690 f6d93710        0 f8fa1764 nfsv3 WRITE a:call_transmit_status q:none
  5609 0001    -11 eeb42690 f6d937e0        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5610 0001    -11 eeb42690 f6d93230        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5611 0001    -11 eeb42690 f6d93300        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5612 0001    -11 eeb42690 f6d93090        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5613 0001    -11 eeb42690 f6d933d0        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5614 0001    -11 eeb42690 f6d93cc0        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5615 0001    -11 eeb42690 f6d93a50        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5616 0001    -11 eeb42690 f6d93640        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5617 0001    -11 eeb42690 f6d93b20        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending
  5618 0001    -11 eeb42690 f6d93160        0 f8fa1764 nfsv3 WRITE a:call_status q:xprt_sending

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>