Fixes for FreeBSD deprovision

When removing the previously provisioned user the 'rmuser' command wants
to kill all processes that are owned by the user, but this kills the
user's shell and 'waagent -deprovision+user' command before we're able
to properly deprovision.  We fix this by moving the DeleteAccount()
routing a bit lower in Deprovision(), and run rmuser in a detached
process to prevent it from killing our python script.
change hard code wala configure path to MyDistro.getConfigurationPath() and ignore exception when get ctime of the configure file
Merge pull request #55 from qingfuwang/2.0

change hard code wala configure path to MyDistro.getConfigurationPath() ...
Merge pull request #53 from szarkos/FreeBSD-deprovision

Fixes for FreeBSD deprovision
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