Focus buddy list window before trying to access the tools menu in pidgin.feature

Originally created by @kytv on #10217 (Redmine)

    Then Pidgin successfully connects to the "irc.oftc.net" account                                              # features/step_definitions/pidgin.rb:296
calling as amnesia: xdotool search --name '.*oftc\.net$' windowactivate --sync
call returned: [0, "", ""]
    And I can join the "#tails" channel on "irc.oftc.net"                                                        # features/step_definitions/pidgin.rb:339
calling as root: sysctl -w kernel.printk_ratelimit=0
call returned: [0, "kernel.printk_ratelimit = 0\n", ""]
calling as root: date
call returned: [0, "Thu Sep 17 18:43:10 UTC 2015\n", ""]
    Given I start monitoring the AppArmor log of "/usr/bin/pidgin"                                               # features/step_definitions/common_steps.rb:1110
calling as amnesia: cp "/usr/share/ca-certificates/spi-inc.org/spi-cacert-2008.crt" "/home/amnesia/.gnupg/test.crt"
call returned: [0, "", ""]
    Then I cannot add a certificate from the "/home/amnesia/.gnupg" directory to Pidgin                          # features/step_definitions/pidgin.rb:414
      FindFailed: can not find PidginToolsMenu.png on the screen.
      Line ?, in File ? (RuntimeError)
      features/pidgin.feature:116:in `Then I cannot add a certificate from the "/home/amnesia/.gnupg" directory to Pidgin'
    And AppArmor has denied "/usr/bin/pidgin" from opening "/home/amnesia/.gnupg/test.crt"                       # features/step_definitions/common_steps.rb:1122
    When I close Pidgin's certificate import failure dialog                                                      # features/step_definitions/pidgin.rb:426
    And I close Pidgin's certificate manager                                                                     # features/step_definitions/pidgin.rb:420
    Given I restart monitoring the AppArmor log of "/usr/bin/pidgin"                                             # features/step_definitions/common_steps.rb:1110
    Then I cannot add a certificate from the "/live/persistence/TailsData_unlocked/gnupg" directory to Pidgin    # features/step_definitions/pidgin.rb:414
    And AppArmor has denied "/usr/bin/pidgin" from opening "/live/persistence/TailsData_unlocked/gnupg/test.crt" # features/step_definitions/common_steps.rb:1122
    When I close Pidgin's certificate import failure dialog                                                      # features/step_definitions/pidgin.rb:426
    And I close Pidgin's certificate manager                                                                     # features/step_definitions/pidgin.rb:420
    Then I can add a certificate from the "/home/amnesia" directory to Pidgin                                    # features/step_definitions/pidgin.rb:406

In the screenshot the conversation window is covering the Buddy List.

Feature Branch: kytv:bugfix/10217-focus-pidgin-buddy-list_before-using-menu