[tests]:add coverage for config/main/utilities_common module

[lguohan]

generate xml, html and term report

Signed-off-by: Guohan Lu lguohan@gmail.com

- What I did
generate xml, html and term report

- How I did it
modify pytest.ini

- How to verify it
check the report. below is the term report. xml/html has lots of more details.

---------- coverage: platform linux2, python 2.7.16-final-0 ----------
Name                              Stmts   Miss  Cover
-----------------------------------------------------
config/__init__.py                    0      0   100%
config/aaa.py                       132     82    38%
config/config_mgmt.py               345    116    66%
config/feature.py                    25      5    80%
config/main.py                     2280   1683    26%
config/mlnx.py                      134     93    31%
config/nat.py                       680    570    16%
show/__init__.py                      0      0   100%
show/bgp_frr_v4.py                   36     36     0%
show/bgp_frr_v6.py                   33     33     0%
show/bgp_quagga_v4.py                20     20     0%
show/bgp_quagga_v6.py                15     15     0%
show/feature.py                      34      0   100%
show/main.py                       1892   1359    28%
show/mlnx.py                         80     62    23%
utilities_common/__init__.py          0      0   100%
utilities_common/cli.py              26      9    65%
utilities_common/db.py                5      0   100%
utilities_common/intf_filter.py      30     18    40%
utilities_common/netstat.py          35     15    57%
utilities_common/util_base.py        32     32     0%
-----------------------------------------------------
TOTAL                              5834   4148    29%
Coverage HTML written to dir htmlcov
Coverage XML written to file coverage.xml

- Previous command output (if the output of a command-line utility has changed)

- New command output (if the output of a command-line utility has changed)

[lguohan]

let's start from these modules.

[lguohan]

failure not related to this pr.

[lguohan]

coverage data is available now.

https://sonic-jenkins.westus2.cloudapp.azure.com/job/common/job/sonic-utilities-build/

the detailed report is here.

https://sonic-jenkins.westus2.cloudapp.azure.com/job/common/job/sonic-utilities-build/RCov_20Report/

can you also drill down to each line.