Create rally report dir in root before running Rally, Tempest

If the lab was deployed in the pipeline, the /root does not
contain the /root/rally_reports/ directroy. But the /root is
mounted before running tests and everywhere there is a hard-code
that repors are saved in rally_reports/ folder.

If the /root/rally_reports/ dir already exists (and even contains
some files) - it is not overwritten and the files inside are not
deleted.

Change-Id: I22ad423580d2f7cd08ac8b619cb39e0e60400d95
diff --git a/src/com/mirantis/mk/Test.groovy b/src/com/mirantis/mk/Test.groovy
index f2fcc7e..1ac19cc 100644
--- a/src/com/mirantis/mk/Test.groovy
+++ b/src/com/mirantis/mk/Test.groovy
@@ -51,6 +51,7 @@
 def runTempestTests(master, dockerImageLink, target, pattern = "false", logDir = "/home/rally/rally_reports/",
                     doCleanupResources = "false") {
     def salt = new com.mirantis.mk.Salt()
+    salt.runSaltProcessStep(master, target, 'file.mkdir', ["/root/rally_reports"])
     if (pattern == "false") {
         salt.cmdRun(master, "${target}", "docker run --rm --net=host " +
                                          "-e TEMPEST_CONF=mcp.conf " +
@@ -85,6 +86,7 @@
 def runRallyScenarios(master, dockerImageLink, target, scenario, logDir = "/home/rally/rally_reports/",
                       doCleanupResources = "false", containerName = "rally_ci") {
     def salt = new com.mirantis.mk.Salt()
+    salt.runSaltProcessStep(master, target, 'file.mkdir', ["/root/rally_reports"])
     salt.cmdRun(master, target, "docker run --net=host -dit " +
                                 "--name ${containerName} " +
                                 "-e SOURCE_FILE=keystonercv3 " +