tests/fusefs: fix all tests that depend on kern.maxphys

[glebius]

Summary

The tests try to read kern.maxphys sysctl into int value, while
unsigned long is required. Not sure when this was broken, seems like
since cd8537910406e.

[kib]

u_long

tests/sys/fs/fusefs/write.cc

182

This is getting close to a fence, and probably over it with custom maxphys setting.

[glebius]

In D45053#1027303, @kib wrote:

u_long

The whole test set doesn't use this style, that's why I used unsigned long. I'd leave this decision to Alan.

[asomers]

tests/sys/fs/fusefs/write.cc

182

What do you mean by "fence"?

[kib]

tests/sys/fs/fusefs/write.cc

182

I mean that it is not too far from the default MAXPHYS value, and since maxphys is the dynamic boot parameter, user might cause the maxhphys to exceed m_maxwrite unknowingly.

[asomers]

tests/sys/fs/fusefs/write.cc

182

Ok, fair point. We can change the expression to "2 * m_maxphys". I can do that in a follow up if @glebius doesn't.