EntityResolver should check the classpath

[nvoxland]

Even if the standard ResourceAccessor does not include it.

Fixes #1609

[codecov]

Codecov Report

Merging #1621 (800d1ea) into 4.3.x (18202bc) will increase coverage by 0.02%.
The diff coverage is 34.49%.

@@             Coverage Diff              @@
##              4.3.x    #1621      +/-   ##
============================================
+ Coverage     49.59%   49.62%   +0.02%     
- Complexity     7862     7880      +18     
============================================
  Files           757      759       +2     
  Lines         37024    37133     +109     
  Branches       6699     6726      +27     
============================================
+ Hits          18363    18427      +64     
- Misses        16231    16248      +17     
- Partials       2430     2458      +28     

Impacted Files	Coverage Δ	Complexity Δ
...uibase-core/src/main/java/liquibase/Liquibase.java	40.07% <0.00%> (+0.19%)	58.00 <0.00> (+1.00)
.../main/java/liquibase/change/AbstractSQLChange.java	82.03% <0.00%> (ø)	29.00 <0.00> (ø)
...quibase/change/core/ExecuteShellCommandChange.java	15.38% <ø> (ø)	13.00 <0.00> (ø)
.../java/liquibase/database/core/Ingres9Database.java	26.31% <0.00%> (ø)	8.00 <0.00> (ø)
...main/java/liquibase/datatype/core/BooleanType.java	19.44% <0.00%> (ø)	10.00 <0.00> (ø)
...e/src/main/java/liquibase/example/StartH2Main.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../liquibase/hub/listener/HubChangeExecListener.java	14.81% <0.00%> (-0.24%)	11.00 <0.00> (ø)
...n/java/liquibase/integration/commandline/Main.java	25.02% <0.00%> (-0.03%)	138.00 <0.00> (ø)
.../liquibase/integration/spring/SpringLiquibase.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../java/liquibase/parser/ChangeLogParserFactory.java	93.33% <ø> (ø)	13.00 <0.00> (ø)
... and 49 more

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