nsfarm/board: wait for boot longer

This is to support HBD that right now boots way longer.
Waiting four minutes for boot is very long time but for testing it is
reasonable to margin for boot.

nsfarm/board/_board.py

@@ -86,7 +86,7 @@ class Board(abc.ABC):
             uboot.run('setenv serverip 192.168.1.1')
             self._board_bootup(uboot)
         # Wait for bootup
-        self._pexpect.expect_exact(["Router Turris successfully started.", ], timeout=120)
+        self._pexpect.expect_exact(["Router Turris successfully started.", ], timeout=240)
         # Note Shell sends new line which opens terminal for it
         shell = cli.Shell(self._pexpect)
         shell.run("sysctl -w kernel.printk='0 4 1 7'")  # disable kernel print to not confuse console flow