Simplification to the CRIU configure.m4 script:

 * Remove redundant/unnecessary uses of $2
 * Change a bunch of logic from negative to positive
 * Use OPAL_VAR_SCOPE_PUSH/POP to help reduce env var usage
 * Only use "" in test statements with strings that require sanitization
 * Removed redundant AC_MSG_WARN/ERROR.  There's now only one check at
   the bottom for whether the component is "good" or not.  We'll
   AC_MSG_WARN/ERROR in that one location.