Ignore network blocks that have invalid WEP key length

Ignore network blocks that have invalid WEP key length

Do not try to associate with a network that has an invalid or incomplete
configuration because the association or at least data connection would
fail anyway. This commits adds a common function for checking whether a
network block is disabled to make it easier to check network blocks
without having to reject them during configuration file parsing (which
would prevent wpa_supplicant from starting). The only additional check
added in this commit is to verify the WEP key length. Similar checks for
other parameters can be added in future commits.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>