Remove cpl7 unit tests

[billsacks]

In trying to get the unit tests running on derecho, I ran into problems with the cpl7 unit tests. It seems like these aren't useful anymore: they at least aren't useful to CESM; @rljacob are they useful to E3SM?

Test suite: Just ran ./scripts_regression_tests.py test_sys_unittest.py - on derecho, cheyenne and my mac. I ran in the context of CTSM master. This needed changes in the share code and ccs_config (in separate PRs that I am opening) - but it won't do any harm to bring in this cime change separately from those (the others are just needed for unit tests to pass on derecho).
Test baseline: N/A
Test namelist changes: none
Test status: bit for bit

Fixes none

User interface changes?: N

Update gh-pages html (Y/N)?: N

[billsacks]

A bit more details: the issue I ran into on derecho was in the build of mpi-serial for the unit tests; we needed to build mpi-serial in order to build mct, and needed to build mct in order to build the cpl7 unit tests. On derecho, I got this and many similar errors:

/glade/work/sacks/ctsm_code/ctsm/libraries/mct/mpi-serial/send.c:218:1: error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Wimplicit-int]

I haven't spent any time trying to resolve that issue, but figured that the cpl7 unit tests may not be worth maintaining at this point. But @rljacob if you feel differently, I can try to dig into this a bit.

[jedwards4b]

You need to set the flags:
-Wno-error=implicit-int
-Wno-error=implicit-function-declaration

For the intel c compiler (and I think any other llvm based compiler).

[rljacob]

No we don't run those cpl7 unit tests. I'm fine with removing them from this file.

[billsacks]

Thanks @jedwards4b and @rljacob . @jedwards4b thanks for the tip on how to get around this issue, but since these unit tests are no longer important to either CESM or E3SM, it seems like the best approach is just to stop running them so we don't need to try to maintain them moving forward. Do you agree?

[jedwards4b]

I do, thank you.