lib: Add zero padding field to flow_wildcards.

lib: Add zero padding field to flow_wildcards.

Before this commit, the compiler would add two bytes of padding to
the 'flow_wildcards' structure to achieve 32bit alignment.  These
two bytes had inconsistent values which caused 'flow_wildcards_hash'
to behave inconsistently.  This commit explicitly 32bit aligns
'flow_wildcards' with zero padding.

This commit also fixes an issue where in-band rules were not
getting deleted when in-band control was disabled.