test: CINIT_FLAG_NO_MON_CONFIG or NO_DEFAULT_CONFIG_FILE

test: CINIT_FLAG_NO_MON_CONFIG or NO_DEFAULT_CONFIG_FILE

Usually we use NO_DEFAULT_CONFIG_FILE, but for those tests that need the
plugin directory overrides in order to work properly when run manually
(e.g., "bin/unittest_compression"), read the config and only skip the
mon config.

The NO_DFEAULT_CONFIG_FILE (which also skips the mon) would work for
everything when run via ctest, but as a dev one often runs the unittest
manually and having to pass CEPH_LIB=lib is annoying.  Note that
do_cmake.sh already writes out a trivial ceph.conf with these options
set for us.

Signed-off-by: Sage Weil <sage@redhat.com>