support/testing: test_dropbear.py: use a constant for the password

The password is used in multiple places, so add a constant for it instead of
hardcoding it multiple times.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/testing/tests/package/test_dropbear.py

@@ -4,14 +4,15 @@ import infra.basetest
 
 
 class TestDropbear(infra.basetest.BRTest):
+    passwd = "testpwd"
     config = infra.basetest.BASIC_TOOLCHAIN_CONFIG + \
         """
-        BR2_TARGET_GENERIC_ROOT_PASSWD="testpwd"
+        BR2_TARGET_GENERIC_ROOT_PASSWD="{}"
         BR2_SYSTEM_DHCP="eth0"
         BR2_PACKAGE_DROPBEAR=y
         BR2_TARGET_ROOTFS_CPIO=y
         # BR2_TARGET_ROOTFS_TAR is not set
-        """
+        """.format(passwd)
 
     def test_run(self):
         img = os.path.join(self.builddir, "images", "rootfs.cpio")
@@ -20,7 +21,7 @@ class TestDropbear(infra.basetest.BRTest):
                            options=["-initrd", img,
                                     "-net", "nic",
                                     "-net", "user,hostfwd=tcp::2222-:22"])
-        self.emulator.login("testpwd")
+        self.emulator.login(self.passwd)
         cmd = "netstat -ltn 2>/dev/null | grep 0.0.0.0:22"
         _, exit_code = self.emulator.run(cmd)
         self.assertEqual(exit_code, 0)