Fix qstat -u <username>

Commit 556c7ca03636248bdd1582bb5eeffb6e363da930 broke
qstat -u <user>.  This one-liner fixes that.
Only send needed data over the wire for qstat (part 1)

By default, qstat does not specify the attributes it needs.  The
server sends all attribute data over the wire.  On systems with a
large number of jobs OR a large number of nodes, this can be a huge
amount of un-needed data.  Avoid this if possible.
Only send needed data over the wire for qstat (part 2)

Added a new batch request SelStatAttr. This is the same as SelStat
but it includes an attrl to limit what attributes need to be
returned.  qstat is currently the only client that uses this.  If
a new client is talking to an old server, it will fall back to
using SelStat.