Description of problem:
 When customer use PXE and kickstart to install RHEL 7.1 , the installation failed because the wrong size of biosboot partition.

 The size of biosboot partition is set as 1MB in ks.cfg :
~~~
part biosboot --fstype='biosboot' --ondisk=sda --size=1
~~~  
  But the actual size will be 4MiB and will see this information:
~~~
allowable size is 512 KiB to 2048 KiB
~~~
 Then the installation failed.


Version-Release number of selected component (if applicable):
  RHEL 7.1

How reproducible:


Steps to Reproduce:
1. Use 16*600G hard driver set up RAID 1+0, the biosboot partition will be assigned 2MiB size and the install will be completed successfully. 
2. Use 16*600G hard driver set up RAID 0, the biosboot partition will be assigned 4MiB size and the install will be failed. 


Actual results:
  The actual allocation size and settings are inconsistent, the installation failed.

Expected results:
  The biosboot partition assigned size is the same as the setting.