Reordering KextImageInfo::LoadImageUsingMemoryModule

so we only call ModulesDidLoad at the end of the method
after the new module has been added to the target and
the sections have all been adjusted to their actual
load addresses.  Solves a problem where an operating
system plugin in the kernel could be loaded multiple
times; the first before the binary had even been
added to the target.

<rdar://problem/50523558>