Fix resource disk partition format detection (#478)
Fix resource disk partition format detection (#478)

With recent versions of sfdisk the -c command is deprecated and
--part-type is recommended to be used instead. This use also requires
the output to be stripped instead of rstripped due to a leading space.
hglkrijger/WALinuxAgent,hglkrijger/WALinuxAgent,rjschwei/WALinuxAgent,Azure/WALinuxAgent,andyliuliming/WALinuxAgent,rjschwei/WALinuxAgent,andyliuliming/WALinuxAgent,Azure/WALinuxAgent