Use platform agnostic newlines in string formatting

the following

• https://github.com/openmrs/openmrs-core/blob/master/api/src/main/java/org/openmrs/util/HttpClient.java#L81
• https://github.com/openmrs/openmrs-core/blob/master/api/src/main/java/org/openmrs/aop/LoggingAdvice.java#L136

use '\n' in String.format expressions to add newlines which is not a newline on windows. best to use '%n' which will translate into a platform specific newline.

see
https://ci.openmrs.org/sonar/drilldown/issues/1865?&rule=findbugs%3AVA_FORMAT_STRING_USES_NEWLINE&rule_sev=MAJOR