In pkg/apis/extensions/v1beta1/conversion.go,
some conversion code was copied from the
legacy api because Pod conversions cannot be
automatically generated because of something
about deprecatedServiceAccount.

This PR fixes two problems due to that copying.

First, the copied code could drift from its source
To fix that, I replaced the Convert_api_ and Convert_v1
implementations with a call to the original function.
I left a wrapper in case something needed to have
a package-local function name.

Second, the copied Convert_* functions, were copied,
in a way that they refer to other conversion functions
that aren't in the current package.  This prevented
genconverion from working from a clean start
(no conversion_generated.go).  Perhaps the person
who wrote this in the first place had copied
the conversion_generated.go file from legacy,
so it worked.   So, I added the v1
package name to calls to Convert_* functions.
So, when someone Cargo-Cult copies the conversion.go
file, like I did, they now will not have to
wonder why genconversion complains about missing
Convert_ functions.

Deleted the conversion_generated.go and reran genconversion
and it worked, no diffs old vs new conversion_generated.go.