Bug 1564920 - In geckoview-junit tests, do not push profile to existing directory; r=bc

As in bug 1596967, I found that, on the emulator, the check for directory existence
infrequently indicates that a recently created directory does not exist. The following
push() will then adjust its destination directory and push to the wrong location;
without a properly installed profile, geckoview crashes. Let's simplify this sequence
by not creating the directory beforehand and letting the push() create it. The profile
directory is a direct child of the test directory -- no need to create parents either.

Differential Revision: https://phabricator.services.mozilla.com/D56789

--HG--
extra : moz-landing-system : lando

testing/mochitest/runjunit.py

@@ -119,7 +119,6 @@ class JUnitTestRunner(MochitestDesktop):
         if self.fillCertificateDB(self.options):
             self.log.error("Certificate integration failed")
 
-        self.device.mkdir(self.remote_profile, parents=True)
         self.device.push(self.profile.profile, self.remote_profile)
         self.log.debug("profile %s -> %s" %
                        (str(self.profile.profile), str(self.remote_profile)))