Description of problem:

Sync and port latest rhel6 firstboot.py logic

related bzs need review after porting:
O 506162,"traceback during firstboot with error of missing module named
O 524811,"firstboot crashes when needs a reboot"
O 594830,"kdump remains enabled"
O 507432,"Module firstboot_kdump does not contain a class named
O 507647,"Can't actually exit firstboot after configuring kdump"
O 507944,"Slight chance for uninitialized self.kdumpEnabled
variable"
O bz676758,"firstboot doesn't recognize the new crashkernel syntax"
O bz598064,"[FEAT RHEL6.1] Configure and enable kdump by default at
O bz619061,"kexec-tools translation is not Working in Firstboot in any
O bz654245,"firstboot gives ""Insufficient memory to configure kdump!""
O bz688150,"Firstboot - Closing an window is accepted as ""Yes"""
O bz523092,"[RHEL6] Enable kexec-kdump on systems with enough of memory
  (>4G)"
O bz652724,"""Insufficient memory to configure kdump!"" during install"

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