Increase gvfs-test timeout

The current value is not enough and results are sometime flaky on slow architectures

Example of an Ubuntu failing on arm https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-hirsute/hirsute/arm64/g/gvfs/20210107_012602_1fe67@/log.gz

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FAIL: test_media_player (__main__.Drive)
drive mount: media player
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Traceback (most recent call last):
  File "/home/gvfs-testbed-script", line 1272, in test_media_player
    self.assertRegex(out, 'Volume added:\s+.*bogus-cd')
AssertionError: Regex didn't match: 'Volume added:\\s+.*bogus-cd' not found in "Drive connected:    'Linux scsi_debug'\n  Drive(0): Linux scsi_debug\n    Type: GProxyDrive (GProxyVolumeMonitorUDisks2)\n    ids:\n     unix-device: '/dev/sda'\n    themed icons:  [drive-harddisk-solidstate]  [drive-harddisk]  [drive]  [drive-harddisk-solidstate-symbolic]  [drive-harddisk-symbolic]  [drive-symbolic]\n    symbolic themed icons:  [drive-harddisk-solidstate-symbolic]  [drive-harddisk-symbolic]  [drive-symbolic]  [drive-harddisk-solidstate]  [drive-harddisk]  [drive]\n    is_removable=0\n    is_media_removable=0\n    has_media=1\n    is_media_check_automatic=1\n    can_poll_for_media=0\n    can_eject=0\n    can_start=0\n    can_stop=0\n    start_stop_type=shutdown\n    sort_key=01hotplug/1609982702640432\n\nDrive disconnected: 'Linux scsi_debug'\n  Drive(0): Linux scsi_debug\n    Type: GProxyDrive (GProxyVolumeMonitorUDisks2)\n    ids:\n     unix-device: '/dev/sda'\n    themed icons:  [drive-harddisk-solidstate]  [drive-harddisk]  [drive]  [drive-harddisk-solidstate-symbolic]  [drive-harddisk-symbolic]  [drive-symbolic]\n    symbolic themed icons:  [drive-harddisk-solidstate-symbolic]  [drive-harddisk-symbolic]  [drive-symbolic]  [drive-harddisk-solidstate]  [drive-harddisk]  [drive]\n    is_removable=0\n    is_media_removable=0\n    has_media=1\n    is_media_check_automatic=1\n    can_poll_for_media=0\n    can_eject=0\n    can_start=0\n    can_stop=0\n    start_stop_type=shutdown\n    sort_key=01hotplug/1609982702640432\n\n"

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Doing some debugging the log is updated after the current 0.2s delay