setarch: fix personality syscall return code check

setarch: fix personality syscall return code check

Depending on architecture and kernel version, personality
syscall is either capable or incapable of returning an error.
If the return value is not an error, then it's the previous
personality value, which can be an arbitrary value
undistinguishable from an error value.
To make things clear, a second call is needed.

For more details about personality syscall peculiarities see
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=glibc-2.22-637-ge0043e17dfc5

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>