The connection initiation code for "ssh" transport tried to absorb
differences between the stock "ssh" and Putty-supplied "plink" and
its derivatives, but the logic to tell that we are using "plink"
variants were too loose and falsely triggered when "plink" appeared
anywhere in the path (e.g. "/home/me/bin/uplink/ssh").

* bc/connect-plink:
  connect: improve check for plink to reduce false positives
  t5601: fix quotation error leading to skipped tests
  connect: simplify SSH connection code path