tests: lib: lte_lc_api: Extending test coverage

Adding more test coverage to have 100% function coverage
and increasing branch coverage of the library from ~69% to 82%
by testing ~100 more branches out of the ~870.

Signed-off-by: Tommi Rantanen <[email protected]>

Author: trantanen

tests/lib/lte_lc_api/prj.conf

@@ -18,6 +18,7 @@ CONFIG_AT_MONITOR_HEAP_SIZE=2048
 
 CONFIG_MOCK_NRF_MODEM_AT=y
 CONFIG_MOCK_NRF_MODEM_AT_SCANF_VARGS_COUNT=17
+CONFIG_MOCK_NRF_MODEM_AT_SCANF_VARGS_STR_SIZE=32
 
 # Enable logs if you want to explore them
 #CONFIG_LOG=y