Unable to build disk images when FIPS is enabled on the build system

Issue

When executing lorax-composer on a FIPS system to build a disk image, the tool fails when python3-blivet's md5_file() function is called:

File "/usr/lib/python3.6/site-packages/blivet/mounts.py", line 109, in get_mountpoints
  self._cache_check()
File "/usr/lib/python3.6/site-packages/blivet/mounts.py", line 171, in _cache_check
  md5hash = util.md5_file("/proc/mounts")
File "/usr/lib/python3.6/site-packages/blivet/util.py", line 574, in md5_file
  md5 = hashlib.md5()
ValueError: [digital envelope routines: EVP_DigestInit_ex] disabled for FIPS