This change makes ironic-lib consistent with ironic-python-agent
and diskimage-builder's defaults for ESP partition sizes.
The following fedora change lays out why this is a necessary
change: https://fedoraproject.org/wiki/Changes/BiggerESP
In summary, additional space is needed if OS driven firmware
flashing is going to take place, and unikernels + next generation
bootloaders are going to consume more space than the existing
grub loader has.
Change-Id: I4fc63c02bf57a08e75121cfa1fd35a56c0427553
2f7f72e147