Move slapi_pblock_set_flag_operation_notes() to slapi-plugin.h

[mreynolds389]

Issue Description

slapi_pblock_set_flag_operation_notes() is currently only available in slapi-private.h, but with the latest changes at add "notes=M" it needs to be available to plugins.

[droideck]

#6112

[mreynolds389]

2003e37..ca37886 389-ds-base-3.0 -> 389-ds-base-3.0
bf03653..3f74a66 389-ds-base-2.5 -> 389-ds-base-2.5
f52c5f2..6586fbe 389-ds-base-2.4 -> 389-ds-base-2.4