xexec operation type and nesting

[niam]

If methods of the caller object affected by xexec hooks might be called in a hook then operation type will be overwritten. For instance, if in pre-exec hook method of the caller object will invoke another method that will overwrite operation type, the post-exec hook of former caller will receive wrong operation type.

Hook should receive operation type as a function argument.

[niam]

(In [f9ff4b609fb8825e71b80b0e4c6c328bd901f449]) {issue #70[fixed]} xexec hooks get operation type as a function argument