Improve Linux arm32/arm64 corefx test runs.

Add proper parallelism.

Prevent per-test output during parallel runs from interleaving
by saving output per process and displaying it after the
process has completed.

Improve summary test/failure output at end of log.

Change Linux arm32/arm64 corefx jobs to run tests in parallel.

Change Linux/arm64 corefx scheduled jobs to be daily, not weekly,
since they are very fast when run in parallel (<20 minutes).

netci.groovy

@@ -1586,10 +1586,8 @@ def static addNonPRTriggers(def job, def branch, def isPR, def architecture, def
                 break
             }
             if (jobRequiresLimitedHardware(architecture, os)) {
-                if ((architecture == 'arm64') && (os == 'Ubuntu16.04') && !isCoreFxScenario(scenario)) {
+                if ((architecture == 'arm64') && (os == 'Ubuntu16.04')) {
                     // These jobs are very fast on Linux/arm64 hardware, so run them daily.
-                    // TODO: When the corefx jobs are made to run in parallel, run those
-                    // jobs daily as well.
                     addPeriodicTriggerHelper(job, '@daily')
                 }
                 else {
@@ -3452,7 +3450,7 @@ def static CreateOtherTestJob(def dslFactory, def project, def branch, def archi
 
             if (doCoreFxTesting) {
                 shell("""\
-\${WORKSPACE}/tests/scripts/run-corefx-tests.sh --sequential --test-exclude-file \${WORKSPACE}/tests/${architecture}/corefx_linux_test_exclusions.txt --runtime \${WORKSPACE}/${workspaceRelativeFxRootLinux}/bin/testhost/netcoreapp-Linux-Release-${architecture} --arch ${architecture} --corefx-tests \${WORKSPACE}/${workspaceRelativeFxRootLinux}/bin --configurationGroup Release""")
+\${WORKSPACE}/tests/scripts/run-corefx-tests.sh --test-exclude-file \${WORKSPACE}/tests/${architecture}/corefx_linux_test_exclusions.txt --runtime \${WORKSPACE}/${workspaceRelativeFxRootLinux}/bin/testhost/netcoreapp-Linux-Release-${architecture} --arch ${architecture} --corefx-tests \${WORKSPACE}/${workspaceRelativeFxRootLinux}/bin --configurationGroup Release""")
             }
             else {
                 def runScript = "${dockerCmd}./tests/runtest.sh"