drwrap-test failed on Appveyor 32-bit: 2nd library load missing some callbacks

The drwrap-test failed once in PR #4230 on 32-bit Appveyor in a strange way. On the 2nd library load, most of the wrap callbacks were not called. I can't reproduce this locally: ran 500x. On Appveyor it did not reproduce.

https://ci.appveyor.com/project/DynamoRIO/dynamorio/builds/31767039
```
thread.appdll process init

in level0 42

in level1 42 1111


in level2 1153



level1 returned -4

level0 returned 42

skipme returned 7 and x=3

in repeatme with arg 3


in repeatme with arg 2

repeatme returned 2
replaceme returned 0 and x=6
replaceme2 returned 1 and x=999
replace_callsite returned 2 and x=777

in preonly
in postonly

in skipme
in postonly







in runlots 1024


long0 A


long1 A


long2 A


long3 A








longdone


called_indirectly_subcall 43

called_indirectly 42 => 44


print_from_asm 1

print_from_asm 7


loaded library
thread.appdll process init
in level0 37
in level1 37 74
in level2 111
level1 returned 37
level0 returned 37
in skipme
skipme returned -1 and x=4
in repeatme with arg 4
repeatme returned 4
replaceme returned 0 and x=6
replaceme2 returned 1 and x=999
replace_callsite returned 2 and x=777
in preonly
in postonly
in skipme
in postonly







in runlots 1024

long0 A

long1 A

long2 A

long3 A




longdone
called_indirectly_subcall 43
called_indirectly 42 => 44
print_from_asm 1
print_from_asm 7
loaded library
thank you for testing the client interface
all done
```