oeqa/core/context: initialize _run_end_time

with _run_start_time as value. For partial results of interrupted runs,
this info might be otherwise missing for at least one testcase

(From OE-Core rev: 1c5e8baf57fa2a33b9ef507b11d9ea9acaa77238)

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/core/context.py

@@ -85,6 +85,7 @@ class OETestContext(object):
         self.skipTests(skips)
 
         self._run_start_time = time.time()
+        self._run_end_time = self._run_start_time
         if not processes:
             self.runner.buffer = True
         result = self.runner.run(self.prepareSuite(self.suites, processes))