p9: fix lcreate to respect the open mode
p9: fix lcreate to respect the open mode

lcreate is not just used for creat(2), but open(2) as well. So it is
possible that the read/write mode is specified manually.

BUG=chromium:1105484
TEST=Run the test program in the bug. Read returns 0 like on other
     filesystem.

Change-Id: I4fb642deb09831f00d3bd83e973e8a42c54ec5d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2297228
Tested-by: Victor Hsieh <e50b749460aecb2d84d38a0c40b84707be8ae902@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Chirantan Ekbote <35787c0e27de5c48735e07f8324823b765e8bcbc@chromium.org>
Auto-Submit: Victor Hsieh <e50b749460aecb2d84d38a0c40b84707be8ae902@chromium.org>
Commit-Queue: Victor Hsieh <e50b749460aecb2d84d38a0c40b84707be8ae902@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm