iflib: hold the CTX lock in iflib_pseudo_register

[jacob.e.keller_intel.com]

Summary

The iflib_device_register function takes the CTX lock before calling
IFDI_ATTACH_PRE, and releases it upon finishing the registration.

Mirror this process in iflib_pseudo_register, so that we always hold the
CTX lock during the attach process when registering a pseudo interface
or a regular interface.

This was caught by code inspection while attempting to analyze where the
CTX lock was held.

Signed-off-by: Jacob Keller <[e-mail]>

[erj]

Anyone else have any feedback? It makes sense to me that the attach process for pseudo devices should use the context lock like the attach process for regular devices.

[shurd]

Looks good to me.