Fix logic in zigbee wrapper to correctly evaluate boolean values.

Fix logic in zigbee wrapper to correctly evaluate boolean values.

Boolean values could be read as either "0" or "00" and thus a simple
strcmp with "0" would not suffice.
Additionally, sometimes, bitmasks are read and so we need the entire
numeric value of the string.

Changed strcmp operations to convert to numeric operations.
Also extracted duplicate code into it's own function

Change-Id: I9ab20ba5b4f2e9eb335a9dd51503fe19ceca7158
Signed-off-by: Mandeep Shetty <mandeep.shetty@intel.com>
Signed-off-by: Joseph Morrow <joseph.l.morrow@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3157
Reviewed-by: Joseph Morrow <joseph.l.morrow@intel.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3525