TRQ-1260: qdel clientretry support

Added clientretry feature as it works in qsub:
* -b <num> command line argument support;
* CLIENTRETRY configuration option support;
* PBS_CLIENTRETRY environment variable support.
Clientretry allows try to connect to the server in a loop during the
given time period.

Added 3-times retry to send the general command (delete task) to the
server as it implemented in qsub, see TRQ-2417.

Added unit test.

Removed server code duplicate from qsub.
Merge pull request #247 from DSRCompany/TRQ-1260_qdel_clientretry_support

TRQ-1260: qdel clientretry support
TRQ-2736. Fix a host detection issue with pbsdsh/tm interface.

When using pbsdsh, fix assumptions where pbs_mom incorrectly determined
which host was being used. pbs_mom's checks didn't really work if you
are running more than one task per node at a time. This caused hangs
when running pbsdsh utilities.