core: use return value instead of a shared boolean in recovery

This patch adds the use of return value to return whether reconstruct command got
to execute ReconstructMasterVDS, rather then use a shared boolean -  this allows
also to execute reconstruct from recovery as internal command rather then
super.execute()  which is less trivial and can cause to some issues.

NOTE: execution of reconstruct from recovery was reverted in commit
I9423d880a7d10a5bfa917e415fe41651f9d7e7f1 because of some issues that it
caused, this patch fixes those issues.

Change-Id: I880361ebe3f23a098a4ede760310c1f0148ae5c6
Signed-off-by: Liron Aravot <laravot@redhat.com>