KVM: selftests: memslot_perf_test: increase guest sync timeout

When memslot_perf_test is run nested, first iteration of test_memslot_rw_loop
testcase, sometimes takes more than 2 seconds due to build of shadow page tables.

Following iterations are fast.

To be on the safe side, bump the timeout to 10 seconds.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Tested-by: Liam Merwick <liam.merwick@oracle.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Link: https://lore.kernel.org/r/20241004220153.287459-1-mlevitsk@redhat.com


Signed-off-by: Sean Christopherson <seanjc@google.com>