LU-15559 tests: add do_node_vp() and do_facet_vp()

LU-15559 tests: add do_node_vp() and do_facet_vp()

Add new test-framework functions (do_node_vp() and do_facet_vp())
which carefully escape and quote command lines for execution on the
local or remote node. Add sanityn test_0 to verify.

Lustre-change: https://review.whamcloud.com/46535

Test-Parameters: trivial env=ONLY="0" testlist=sanityn
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: Ic491b0148e6ef11ecd0b3ccce983afcf4d1300e5
Reviewed-on: https://review.whamcloud.com/46537
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>