ANDROID: Incremental fs: Separate pseudo-file code

Also fixed two bugs in the process:

is_pseudo_filename was not previously checking for .log, so an attempt
to create a .log would succeed.

All ioctls could be called on all files. ioctls now set on the correct
files.

Bug: 162856396
Test: incfs_test passes
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Change-Id: I3f1e87d018836f51a97897880dd70181db4f7169