Added "survival after connection cycle check" testcases

Added "survival after connection cycle check" testcases

After something was committed into the datastore, the
first test case gracefully disconnects (and fails if that
turned out to be impossible), the second one then checks
through restconf that the added item is still there,
the third one reconnects (and fails if the device turned
out to be inaccessible through netconf) and the fourth one
checks that the thing is still sitting there in the Netconf
data store.

Change-Id: I8898a9e498d862cce6b811b44d3c4d0b0194390f
Signed-off-by: Jozef Behran <jbehran@cisco.com>